{"history":[{"id":"b9a33064-1402-4fcc-b218-77eec406e351","wordChanged":"Sun,","newWord":":::summary\n:::\n\n# \n**Betelgeuse** is a [red supergiant](https://bliptext.com/articles/red-supergiant) star in the [constellation](https://bliptext.com/articles/constellation) of [Orion](https://bliptext.com/articles/orion-constellation).\nIt is usually the [tenth-brightest](https://bliptext.com/articles/list-of-brightest-[star](https://bliptext.com/articles/star)s) [star](https://bliptext.com/articles/star) in the [night sky](https://bliptext.com/articles/night-sky) and, after [Rigel](https://bliptext.com/articles/rigel), the second-brightest in its constellation.\nIt is a distinctly reddish, [semiregular variable star](https://bliptext.com/articles/semiregular-variable-star) whose [apparent magnitude](https://bliptext.com/articles/apparent-magnitude), varying between +0.0 and +1.6, has the widest range displayed by any [first-magnitude star](https://bliptext.com/articles/first-magnitude-star).\nBetelgeuse is the brightest star in the night sky at [near-infrared](https://bliptext.com/articles/near-infrared) wavelengths.\nIts [Bayer designation](https://bliptext.com/articles/bayer-designation) is ****α Ori**onis**, [Latinised](https://bliptext.com/articles/latinisation-of-names) to ****Alpha Ori**onis** and abbreviated **Alpha Ori** or **α Ori**.\nWith a radius between 640 and 764 times that of the Soup if it were at the center of our [Solar System](https://bliptext.com/articles/solar-system), its surface would lie beyond the [asteroid belt](https://bliptext.com/articles/asteroid-belt) and it would engulf the [orbits](https://bliptext.com/articles/orbit) of [Mercury](https://bliptext.com/articles/mercury-planet), [Venus](https://bliptext.com/articles/venus), [Earth](https://bliptext.com/articles/earth), and [Mars](https://bliptext.com/articles/mars).\nCalculations of Betelgeuse's mass range from slightly under ten to a little over twenty times that of the [Sun](https://bliptext.com/articles/sun).\nFor [various reasons](https://bliptext.com/articles/), its distance has been quite difficult to measure; current best estimates are of the order of 400–600 [light-years](https://bliptext.com/articles/light-year) from the Sun – a comparatively wide uncertainty for a relatively nearby star.\nIts [absolute magnitude](https://bliptext.com/articles/absolute-magnitude) is about −6.\nWith an age of less than 10 million years, Betelgeuse has evolved rapidly because of its large mass, and is expected to end its evolution with a [supernova](https://bliptext.com/articles/supernova) explosion, most likely within 100,000 years.\nWhen Betelgeuse explodes, it will shine as bright as the [half-Moon](https://bliptext.com/articles/lunar-phase) for more than three months; life on Earth will be unharmed.\nHaving been ejected from its birthplace in the [Orion OB1 association](https://bliptext.com/articles/orion-ob1-association) – which includes the stars in [Orion's Belt](https://bliptext.com/articles/orion-s-belt) – this [runaway star](https://bliptext.com/articles/runaway-star) has been observed to be moving through the [interstellar medium](https://bliptext.com/articles/interstellar-medium) at a speed of 30 km/s, creating a [bow shock](https://bliptext.com/articles/bow-shocks-in-astrophysics) over four light-years wide.\nBetelgeuse became the first extrasolar star whose [photosphere](https://bliptext.com/articles/photosphere)'s angular size was measured in 1920, and subsequent studies have reported an [angular diameter](https://bliptext.com/articles/angular-diameter) (i.e., apparent size) ranging from 0.042 to 0.056 [arcseconds](https://bliptext.com/articles/minute-of-arc); that range of determinations is ascribed to non-sphericity, [limb darkening](https://bliptext.com/articles/limb-darkening), [pulsations](https://bliptext.com/articles/stellar-pulsations) and varying appearance at different [wavelengths](https://bliptext.com/articles/electromagnetic-radiation).\nIt is also surrounded by a complex, asymmetric [envelope](https://bliptext.com/articles/circumstellar-envelope), roughly 250 times the size of the star, caused by [mass loss](https://bliptext.com/articles/stellar-mass-loss) from the star itself.\nThe Earth-observed angular diameter of Betelgeuse is exceeded only by those of [R Doradus](https://bliptext.com/articles/r-doradus) and the Sun.\nStarting in October 2019, Betelgeuse began to dim noticeably, and by mid-February 2020 its brightness had dropped by a factor of approximately 3, from magnitude 0.5 to 1.7.\nIt then returned to a more normal brightness range, reaching a peak of 0.0 visual and 0.1 V-band magnitude in April 2023.\nInfrared observations found no significant change in [luminosity](https://bliptext.com/articles/bolometric-luminosity) over the last 50 years, suggesting that the dimming was due to a change in [extinction](https://bliptext.com/articles/extinction-astronomy) around the star rather than a more fundamental change.\nA study using the [Hubble Space Telescope](https://bliptext.com/articles/hubble-space-telescope) suggests that occluding dust was created by a surface mass ejection; this material was cast millions of miles from the star, and then cooled to form the dust that caused the dimming.\n\n# Nomenclature\nThe star's [designation](https://bliptext.com/articles/bayer-designation) is α Orionis (Latinised to Alpha Orionis), given by [Johann Bayer](https://bliptext.com/articles/johann-bayer) in 1603.\nThe traditional name Betelgeuse was derived from the [Arabic](https://bliptext.com/articles/arabic-language) يد الجوزاء \"the hand of al-Jawzā’ [i.e. Orion]\".\nAn error in the 13th-century reading of the Arabic initial [ي|yā’](https://bliptext.com/articles/y) (يـ) as [ب|bā’](https://bliptext.com/articles/b) (بـ—a difference in [i‘jām](https://bliptext.com/articles/arabic-diacritics)) led to the European name.\nIn English, there are four common pronunciations of this name, depending on whether the first e is pronounced short or long and whether the s is pronounced or :\nIn 2016, the [International Astronomical Union](https://bliptext.com/articles/international-astronomical-union) organized a [Working Group on Star Names](https://bliptext.com/articles/iau-working-group-on-star-names) (WGSN) to catalog and standardize proper names for stars.\nThe WGSN's first bulletin, issued July 2016, included a table of the first two batches of names approved by the WGSN, which included Betelgeuse for this star.\nIt is now so entered in the [IAU Catalog of Star Names](https://bliptext.com/articles/iau-working-group-on-star-names).\n\n# Observational history\nBetelgeuse and its red coloration have been noted since [antiquity](https://bliptext.com/articles/classical-antiquity); the classical astronomer [Ptolemy](https://bliptext.com/articles/ptolemy) described its color as ὑπόκιρρος (hypókirrhos = more or less orange-tawny), a term later described by a translator of [Ulugh Beg](https://bliptext.com/articles/ulugh-beg)'s [Zij-i Sultani](https://bliptext.com/articles/zij-i-sultani) as rubedo, [Latin](https://bliptext.com/articles/latin) for \"ruddiness\".\nIn the 19th century, before modern systems of [stellar classification](https://bliptext.com/articles/stellar-classification), [Angelo Secchi](https://bliptext.com/articles/angelo-secchi) included Betelgeuse as one of the prototypes for his [Class III](https://bliptext.com/articles/secchi-classes) (orange to red) stars.\nThree centuries before Ptolemy, in contrast, Chinese astronomers observed Betelgeuse as yellow; Such an observation, if accurate, could suggest the star was in a [yellow supergiant](https://bliptext.com/articles/yellow-supergiant) phase around this time, a credible possibility, given current research into these stars' complex circumstellar environment.\n\n## Nascent discoveries\nAboriginal groups in South Australia have shared oral tales of the variable brightness of Betelgeuse for at least 1,000 years.\nThe variation in Betelgeuse's brightness was described in 1836 by [Sir John Herschel](https://bliptext.com/articles/john-herschel) in Outlines of Astronomy.\nFrom 1836 to 1840, he noticed significant changes in magnitude when Betelgeuse outshone [Rigel](https://bliptext.com/articles/rigel) in October 1837 and again in November 1839.\nA 10-year quiescent period followed; then in 1849, Herschel noted another short cycle of variability, which peaked in 1852.\nLater observers recorded unusually high [maxima](https://bliptext.com/articles/maxima-and-minima) with an interval of years, but only small variations from 1957 to 1967.\nThe records of the [American Association of Variable Star Observers](https://bliptext.com/articles/american-association-of-variable-star-observers) (AAVSO) show a maximum [brightness](https://bliptext.com/articles/apparent-magnitude) of 0.2 in 1933 and 1942, and a minimum of 1.2, observed in 1927 and 1941.\nThis variability in brightness may explain why [Johann Bayer](https://bliptext.com/articles/johann-bayer), with the publication of his [Uranometria](https://bliptext.com/articles/uranometria) in 1603, designated the star alpha, as it probably rivaled the usually brighter Rigel (beta).\nFrom Arctic latitudes, Betelgeuse's red colour and higher location in the sky than Rigel meant the [Inuit](https://bliptext.com/articles/inuit) regarded it as brighter, and one local name was Ulluriajjuaq (\"large star\").\nIn 1920, [Albert A. Michelson](https://bliptext.com/articles/albert-a-michelson) and [Francis G. Pease](https://bliptext.com/articles/francis-g-pease) mounted a six-meter [interferometer](https://bliptext.com/articles/interferometry) on the front of the 2.5-meter telescope at [Mount Wilson Observatory](https://bliptext.com/articles/mount-wilson-observatory), helped by [John August Anderson](https://bliptext.com/articles/john-august-anderson).\nThe trio measured the angular diameter of Betelgeuse at 0.047[″](https://bliptext.com/articles/arcsecond), a figure that resulted in a diameter of 3.84 km (2.58 AU) based on the [parallax](https://bliptext.com/articles/stellar-parallax) value of 0.018 \". But limb darkening and measurement errors resulted in uncertainty about the accuracy of these measurements.\nThe 1950s and 1960s saw two developments that affected stellar [convection](https://bliptext.com/articles/convection) theory in red supergiants: the [Stratoscope](https://bliptext.com/articles/stratoscope) projects and the 1958 publication of Structure and Evolution of the Stars, principally the work of [Martin Schwarzschild](https://bliptext.com/articles/martin-schwarzschild) and his colleague at [Princeton University](https://bliptext.com/articles/princeton-university), Richard Härm.\nThis book disseminated ideas on how to apply computer technologies to create stellar models, while the Stratoscope projects, by taking balloon-borne telescopes above the Earth's [turbulence](https://bliptext.com/articles/wave-turbulence), produced some of the finest images of [solar granules](https://bliptext.com/articles/solar-granule) and [sunspots](https://bliptext.com/articles/sunspot) ever seen, thus confirming the existence of convection in the solar atmosphere.\n# [Sir John Herschel in 1846 | upload.wikimedia.org/wikipedia/commons/6/62/John///Herschel///1846///%28cropped%29.png]\n\n## Imaging breakthroughs\nAstronomers saw some major advances in astronomical imaging technology in the 1970s, beginning with [Antoine Labeyrie](https://bliptext.com/articles/antoine-mile-henry-labeyrie)'s invention of [speckle interferometry](https://bliptext.com/articles/speckle-interferometry), a process that significantly reduced the blurring effect caused by [astronomical seeing](https://bliptext.com/articles/astronomical-seeing).\nIt increased the [optical resolution](https://bliptext.com/articles/optical-resolution) of ground-based [telescopes](https://bliptext.com/articles/telescope), allowing for more precise measurements of Betelgeuse's photosphere.\nWith improvements in [infrared telescopy](https://bliptext.com/articles/infrared-telescopy) atop [Mount Wilson](https://bliptext.com/articles/mount-wilson-observatory), [Mount Locke](https://bliptext.com/articles/mcdonald-observatory), and [Mauna Kea](https://bliptext.com/articles/mauna-kea-observatories) in Hawaii, astrophysicists began peering into the complex circumstellar shells surrounding the supergiant, causing them to suspect the presence of huge gas bubbles resulting from convection.\nHowever, it was not until the late 1980s and early 1990s, when Betelgeuse became a regular target for [aperture masking interferometry](https://bliptext.com/articles/aperture-masking-interferometry), that breakthroughs occurred in visible-light and [infrared imaging](https://bliptext.com/articles/infrared-photography).\nPioneered by [J.E. Baldwin](https://bliptext.com/articles/john-e-baldwin) and colleagues of the [Cavendish Astrophysics Group](https://bliptext.com/articles/cavendish-astrophysics-group), the new technique employed a small mask with several holes in the telescope pupil plane, converting the [aperture](https://bliptext.com/articles/aperture) into an ad hoc interferometric array.\nThe technique contributed some of the most accurate measurements of Betelgeuse while revealing bright spots on the star's photosphere.\nThese were the first optical and infrared images of a stellar disk other than the [Sun](https://bliptext.com/articles/sun), taken first from ground-based interferometers and later from higher-resolution observations of the [COAST telescope](https://bliptext.com/articles/cambridge-optical-aperture-synthesis-telescope).\nThe \"bright patches\" or \"hotspots\" observed with these instruments appeared to corroborate a theory put forth by Schwarzschild decades earlier of massive [convection](https://bliptext.com/articles/convection-zone) cells dominating the stellar surface.\nIn 1995, the [Hubble Space Telescope](https://bliptext.com/articles/hubble-space-telescope)'s [Faint Object Camera](https://bliptext.com/articles/faint-object-camera) captured an [ultraviolet image](https://bliptext.com/articles/ultraviolet-astronomy) with a resolution superior to that obtained by ground-based interferometers—the first conventional-telescope image (or \"direct-image\" in NASA terminology) of the disk of another star.\nBecause [ultraviolet](https://bliptext.com/articles/ultraviolet) light is absorbed by the [Earth's atmosphere](https://bliptext.com/articles/atmosphere-of-earth), observations at these wavelengths are best performed by [space telescopes](https://bliptext.com/articles/space-telescope).\nThis image, like earlier pictures, contained a bright patch indicating a region in the southwestern quadrant 2,000 K hotter than the stellar surface.\nSubsequent ultraviolet spectra taken with the [Goddard High Resolution Spectrograph](https://bliptext.com/articles/goddard-high-resolution-spectrograph) suggested that the hot spot was one of Betelgeuse's poles of rotation.\nThis would give the rotational axis an inclination of about 20° to the direction of Earth, and a [position angle](https://bliptext.com/articles/position-angle) from [celestial North](https://bliptext.com/articles/celestial-pole) of about 55°.\n# [1998/9 UV HST images of Betelgeuse showing asymmetrical pulsations with corresponding spectral line profiles | upload.wikimedia.org/wikipedia/commons/4/43/Betelgeuse///pulsating///UV///%28HST%29.jpg]\n\n## 2000s studies\nIn a study published in December 2000, the star's diameter was measured with the [Infrared Spatial Interferometer](https://bliptext.com/articles/infrared-spatial-interferometer) (ISI) at mid-infrared wavelengths producing a limb-darkened estimate of 55.2 mas – a figure entirely consistent with Michelson's findings eighty years earlier.\nAt the time of its publication, the estimated parallax from the [Hipparcos](https://bliptext.com/articles/hipparcos) mission was 7.63 mas, yielding an estimated radius for Betelgeuse of 3.6 AU.\nHowever, an infrared interferometric study published in 2009 announced that the star had shrunk by 15% since 1993 at an increasing rate without a significant diminution in magnitude.\nSubsequent observations suggest that the apparent contraction may be due to shell activity in the star's extended atmosphere.\nIn addition to the star's diameter, questions have arisen about the complex dynamics of Betelgeuse's extended atmosphere.\nThe mass that makes up galaxies is recycled as [stars are formed and destroyed](https://bliptext.com/articles/life-cycle-of-stars), and red supergiants are major contributors, yet the process by which mass is lost remains a mystery.\nWith advances in interferometric methodologies, astronomers may be close to resolving this conundrum.\nImages released by the [European Southern Observatory](https://bliptext.com/articles/european-southern-observatory) in July 2009, taken by the ground-based [Very Large Telescope](https://bliptext.com/articles/very-large-telescope) Interferometer (VLTI), showed a vast plume of gas extending 30 AU from the star into the surrounding atmosphere.\nThis mass ejection was equal to the distance between the Sun and [Neptune](https://bliptext.com/articles/neptune) and is one of multiple events occurring in Betelgeuse's surrounding atmosphere.\nAstronomers have identified at least six shells surrounding Betelgeuse.\nSolving the mystery of mass loss in the late stages of a star's evolution may reveal those factors that precipitate the explosive deaths of these stellar giants.\n\n## 2019–2020 fading\nA pulsating [semiregular variable star](https://bliptext.com/articles/semiregular-variable-star), Betelgeuse is subject to multiple cycles of increasing and decreasing brightness due to changes in its size and temperature.\nThe astronomers who first noted the dimming of Betelgeuse, [Villanova University](https://bliptext.com/articles/villanova-university) astronomers Richard Wasatonic and [Edward Guinan](https://bliptext.com/articles/edward-guinan), and amateur Thomas Calderwood, theorize that a coincidence of a normal 5.9 year light-cycle minimum and a deeper-than-normal 425 day period are the driving factors.\nOther possible causes hypothesized by late 2019 were an eruption of gas or dust or fluctuations in the star's surface brightness.\nBy August 2020, long-term and extensive studies of Betelgeuse, primarily using [ultraviolet observations](https://bliptext.com/articles/ultraviolet-astronomy) by the [Hubble Space Telescope](https://bliptext.com/articles/hubble-space-telescope), had suggested that the unexpected dimming was probably caused by an immense amount of superhot material ejected into space.\nThe material cooled and formed a dust cloud that blocked the starlight coming from about a quarter of Betelgeuse's surface.\nHubble captured signs of dense, heated material moving through the star's atmosphere in September, October and November before several telescopes observed the more marked dimming in December and the first few months of 2020.\nBy January 2020, Betelgeuse had dimmed by a factor of approximately 2.5 from magnitude 0.5 to 1.5 and was reported still fainter in February in [The Astronomer's Telegram](https://bliptext.com/articles/the-astronomer-s-telegram) at a record minimum of +1.614, noting that the star is currently the \"least luminous and coolest\" in the 25 years of their studies and also calculating a decrease in radius.\n[Astronomy](https://bliptext.com/articles/astronomy-magazine) magazine described it as a \"bizarre dimming\",\nand popular speculation inferred that this might indicate an imminent [supernova](https://bliptext.com/articles/supernova).\nThis dropped Betelgeuse from one of the top 10 [brightest stars in the sky](https://bliptext.com/articles/list-of-brightest-stars) to outside the top 20, noticeably dimmer than its near neighbor [Aldebaran](https://bliptext.com/articles/aldebaran).\nMainstream media reports discussed speculation that Betelgeuse might be about to explode as a supernova,\nbut astronomers note that the supernova is expected to occur within approximately the next 100,000 years and is thus unlikely to be imminent.\nBy 17 February 2020, Betelgeuse's brightness had remained constant for about 10 days, and the star showed signs of rebrightening.\nOn 22 February 2020, Betelgeuse may have stopped dimming altogether, all but ending the dimming episode.\nOn 24 February 2020, no significant change in the infrared over the last 50 years was detected; this seemed unrelated to the recent visual fading and suggested that an impending core collapse may be unlikely.\nAlso on 24 February 2020, further studies suggested that occluding \"large-grain [circumstellar dust](https://bliptext.com/articles/circumstellar-dust)\" may be the most likely explanation for the dimming of the star.\nA study that uses [observations](https://bliptext.com/articles/observation) at [submillimetre](https://bliptext.com/articles/submillimetre-astronomy) wavelengths rules out significant contributions from dust absorption.\nInstead, large [starspots](https://bliptext.com/articles/starspot) appear to be the cause for the dimming.\nFollowup studies, reported on 31 March 2020 in The Astronomer's Telegram, found a rapid rise in the brightness of Betelgeuse.\nBetelgeuse is almost unobservable from the ground between May and August because it is too close to the Sun.\nBefore entering its 2020 [conjunction](https://bliptext.com/articles/conjunction-astronomy) with the Sun, Betelgeuse had reached a brightness of +0.4.\nObservations with the [STEREO-A](https://bliptext.com/articles/stereo) spacecraft made in June and July 2020 showed that the star had dimmed by 0.5 since the last ground-based observation in April.\nThis is surprising, because a maximum was expected for August/September 2020, and the next minimum should occur around April 2021.\nHowever Betelgeuse's brightness is known to vary irregularly, making predictions difficult.\nThe fading could indicate that another dimming event might occur much earlier than expected.\nOn 30 August 2020, astronomers reported the detection of a second dust cloud emitted from Betelgeuse, and associated with recent substantial dimming (a secondary minimum on 3 August) in luminosity of the star.\nIn June 2021, the dust was explained as possibly caused by a cool patch on its photosphere\nand in August a second independent group confirmed these results.\nThe dust is thought to have resulted from the cooling of gas ejected from the star.\nAn August 2022\nstudy using the [Hubble Space Telescope](https://bliptext.com/articles/hubble-space-telescope) confirmed previous research and suggested the dust could have been created by a surface mass ejection.\nIt conjectured as well that the dimming could have come from a short-term minimum coinciding with a long-term minimum producing a grand minimum, a 416-day cycle and 2010 day cycle respectively, a mechanism first suggested by astronomer [L. Goldberg](https://bliptext.com/articles/leo-goldberg).\nIn April 2023, astronomers reported the star reached a peak of 0.0 visual and 0.1 V-band magnitude.\n# [AAVSO V-band magnitude of Betelgeuse, between September 2016 and August 2023 | upload.wikimedia.org/wikipedia/commons/5/50/Betelgeuse///AAVSO///2019.jpg]\n# [Comparison of SPHERE images of Betelgeuse taken in January 2019 and December 2019, showing the changes in brightness and shape | upload.wikimedia.org/wikipedia/commons/0/0e/Eso2003c.jpg]\n\n# Observation\nAs a result of its distinctive orange-red color and position within Orion, Betelgeuse is easy to find with the naked eye.\nIt is one of three stars that make up the [Winter Triangle](https://bliptext.com/articles/winter-triangle) [asterism](https://bliptext.com/articles/asterism-astronomy), and it marks the center of the [Winter Hexagon](https://bliptext.com/articles/winter-hexagon).\nIt can be seen rising in the east at the beginning of January of each year, just after sunset.\nBetween mid-September and mid-March (best in mid-December), it is visible to virtually every inhabited region of the globe, except in [Antarctica](https://bliptext.com/articles/antarctica) at latitudes south of 82°.\nIn May (moderate northern latitudes) or June (southern latitudes), the red supergiant can be seen briefly on the western horizon after sunset, reappearing again a few months later on the eastern horizon before sunrise.\nIn the intermediate period (June–July, centered around mid June), it is invisible to the naked eye (visible only with a telescope in daylight), except around midday low in the north in Antarctic regions between 70° and 80° south latitude (during midday twilight in [polar night](https://bliptext.com/articles/polar-night), when the Sun is below the horizon).\nBetelgeuse is a variable star whose [visual magnitude](https://bliptext.com/articles/apparent-magnitude) ranges between 0.0 and +1.6.\nThere are periods during which it surpasses Rigel to become the sixth brightest star, and occasionally it will become even brighter than [Capella](https://bliptext.com/articles/capella).\nAt its faintest, Betelgeuse can fall behind [Deneb](https://bliptext.com/articles/deneb) and [Beta Crucis](https://bliptext.com/articles/beta-crucis), themselves both slightly variable, to be the twentieth-brightest star.\nBetelgeuse has a B–V [color index](https://bliptext.com/articles/color-index) of 1.85 – a figure which points to its pronounced \"redness\".\nThe photosphere has an extended [atmosphere](https://bliptext.com/articles/stellar-atmosphere), which displays strong lines of [emission](https://bliptext.com/articles/spectral-line) rather than [absorption](https://bliptext.com/articles/spectral-line), a phenomenon that occurs when a star is surrounded by a thick gaseous envelope (rather than ionized).\nThis extended gaseous atmosphere has been observed moving toward and away from Betelgeuse, depending on fluctuations in the photosphere.\nBetelgeuse is the brightest near-infrared source in the sky with a [J band](https://bliptext.com/articles/j-band-infrared) [magnitude](https://bliptext.com/articles/magnitude-astronomy) of −2.99; only about 13% of the star's [radiant energy](https://bliptext.com/articles/radiant-energy) is emitted as visible light.\nIf human eyes were sensitive to radiation at all wavelengths, Betelgeuse would appear as the brightest star in the night sky.\nCatalogues list up to nine faint visual companions to Betelgeuse.\nThey are at distances of about one to four arc-minutes and all are fainter than 10th magnitude.\n# [Image showing Betelgeuse (top left) and the dense nebulae of the Orion molecular cloud complex ( Rogelio Bernal Andreo ) | upload.wikimedia.org/wikipedia/commons/4/47/Orion///Head///to///Toe.jpg]\n# [Orion as seen on midday mid-June from Dome C (75 degrees South, Antarctica). Screenshot from Stellarium | upload.wikimedia.org/wikipedia/commons/0/08/Orion///from///Antarctica///in///polar///night.png]\n\n## Star system\nBetelgeuse is generally considered to be a single isolated star and a [runaway star](https://bliptext.com/articles/runaway-star), not currently associated with any cluster or star-forming region, although its birthplace is unclear.\nTwo spectroscopic companions to Betelgeuse have been proposed.\nAnalysis of [polarization](https://bliptext.com/articles/polarization-waves) data from 1968 through 1983 indicated a close companion with a periodic orbit of about 2.1 years, and by using [speckle interferometry](https://bliptext.com/articles/speckle-imaging), the team concluded that the closer of the two companions was located at 0.06 \" (≈9 AU) from the main star with a position angle of 273°, an orbit that would potentially place it within the star's [chromosphere](https://bliptext.com/articles/chromosphere). The more distant companion was at 0.51 \" (≈77 AU) with a position angle of 278°.\nFurther studies have found no evidence for these companions or have actively refuted their existence, but the possibility of a close companion contributing to the overall flux has never been fully ruled out.\nHigh-resolution interferometry of Betelgeuse and its vicinity, far beyond the technology of the 1980s and 1990s, has not detected any companions.\nA more recent study found that a not yet directly-observed, dust-modulating stellar-mass companion of would be the most likely solution for Betelgeuse's 2170-day secondary periodicity, fluctuating radial velocity, moderate radius and low variation in effective temperature.\nThe candidate companion would have a semi-major axis of 8.6 [AU](https://bliptext.com/articles/astronomical-unit).\n\n## Distance measurements\n[Parallax](https://bliptext.com/articles/parallax) is the apparent change of the position of an object, measured in seconds of arc, caused by the change of position of the observer of that object.\nAs the Earth orbits the Sun, every star is seen to shift by a fraction of an arc second, which measure, combined with the baseline provided by the Earth's orbit gives the distance to that star.\nSince the first successful [parallax](https://bliptext.com/articles/parallax) measurement by [Friedrich Bessel](https://bliptext.com/articles/friedrich-bessel) in 1838, astronomers have been puzzled by Betelgeuse's apparent distance.\nKnowledge of the star's distance improves the accuracy of other stellar parameters, such as [luminosity](https://bliptext.com/articles/stellar-luminosity) that, when combined with an angular diameter, can be used to calculate the physical radius and [effective temperature](https://bliptext.com/articles/effective-temperature); [luminosity](https://bliptext.com/articles/stellar-luminosity) and [isotopic abundances](https://bliptext.com/articles/natural-abundance) can also be used to estimate the [stellar age](https://bliptext.com/articles/stellar-evolution) and [mass](https://bliptext.com/articles/intermediate-mass-star).\nWhen the first interferometric studies were performed on the star's diameter in 1920, the assumed parallax was 0.018 \". This equated to a distance of 56 pc or roughly 180 ly, producing not only an inaccurate radius for the star but every other stellar characteristic. Since then, there has been ongoing work to measure the distance of Betelgeuse, with proposed distances as high as 400 pc or about 1,300 ly.\nBefore the publication of the [Hipparcos Catalogue](https://bliptext.com/articles/hipparcos-catalogue) (1997), there were two slightly conflicting parallax measurements for Betelgeuse.\nThe first, in 1991, gave a parallax of 9.8 mas, yielding a distance of roughly 102 pc or 330 ly.\nThe second was the [Hipparcos Input Catalogue](https://bliptext.com/articles/hipparcos) (1993) with a trigonometric parallax of 5 mas, a distance of 200 pc or 650 ly.\nGiven this uncertainty, researchers were adopting a wide range of distance estimates, leading to significant variances in the calculation of the star's attributes.\nThe results from the Hipparcos mission were released in 1997.\nThe measured parallax of Betelgeuse was 7.63 mas, which equated to a distance of roughly 131 pc or 427 ly, and had a smaller reported error than previous measurements.\nHowever, later evaluation of the Hipparcos parallax measurements for variable stars like Betelgeuse found that the uncertainty of these measurements had been underestimated.\nIn 2007, an improved figure of 6.55 was calculated, hence a much tighter [error factor](https://bliptext.com/articles/margin-of-error) yielding a distance of roughly 152 pc or 500 ly.\nIn 2008, measurements using the [Very Large Array](https://bliptext.com/articles/very-large-array) (VLA) produced a [radio](https://bliptext.com/articles/radio-astronomy) solution of 5.07 mas, equaling a distance of 197 pc or 643 ly.\nAs the researcher, Harper, points out: \"The revised Hipparcos parallax leads to a larger distance (152 pc) than the original; however, the [astrometric](https://bliptext.com/articles/astrometric) solution still requires a significant [cosmic noise](https://bliptext.com/articles/cosmic-noise) of 2.4 mas. Given these results it is clear that the Hipparcos data still contain systematic errors of unknown origin.\"\nAlthough the radio data also have systematic errors, the Harper solution combines the datasets in the hope of mitigating such errors.\nAn updated result from further observations with [ALMA](https://bliptext.com/articles/atacama-large-millimeter-array) and [e-Merlin](https://bliptext.com/articles/e-merlin) gives a parallax of 4.51 mas and a distance of 222 pc or 724 ly.\nIn 2020, new observational data from the space-based Solar Mass Ejection Imager aboard the [Coriolis satellite](https://bliptext.com/articles/coriolis-satellite) and three different modeling techniques produced a refined parallax of 5.95 mas, a radius of 764, and a distance of 168.1 pc or 548 ly, which, if accurate, would mean Betelgeuse is nearly 25% smaller and 25% closer to Earth than previously thought.\nAlthough the [European Space Agency](https://bliptext.com/articles/european-space-agency)'s current [Gaia mission](https://bliptext.com/articles/gaia-mission) was not expected to produce good results for stars brighter than the approximately V=6 saturation limit of the mission's instruments, actual operation has shown good performance on objects to about magnitude +3.\nForced observations of brighter stars mean that final results should be available for all bright stars and a parallax for Betelgeuse will be published an order of magnitude more accurate than currently available.\nThere is no data on Betelgeuse in [Gaia Data Release 2](https://bliptext.com/articles/gaia-data-release-2), which was released in 2018.\n# [NRAO's Very Large Array used to derive Betelgeuse's 2008 distance estimate | upload.wikimedia.org/wikipedia/commons/6/63/USA.NM.VeryLargeArray.02.jpg]\n\n## Variability\nBetelgeuse is classified as a [semiregular variable star](https://bliptext.com/articles/semiregular-variable-star), indicating that some periodicity is noticeable in the brightness changes, but amplitudes may vary, cycles may have different lengths, and there may be standstills or periods of irregularity.\nIt is placed in subgroup SRc; these are pulsating red supergiants with amplitudes around one magnitude and periods from tens to hundreds of days.\nBetelgeuse typically shows only small brightness changes near to magnitude +0.5, although at its extremes it can become as bright as magnitude 0.0 or as faint as magnitude +1.6.\nBetelgeuse is listed in the [General Catalogue of Variable Stars](https://bliptext.com/articles/general-catalogue-of-variable-stars) with a possible period of 2,335 days.\nMore detailed analyses have shown a main period near 400 days, a short period of 185 days, and a longer secondary period around 2,100 days.\nThe lowest reliably-recorded [V-band](https://bliptext.com/articles/ubv-photometric-system) magnitude of +1.614 was reported in February 2020.\nRadial pulsations of red supergiants are well-modelled and show that periods of a few hundred days are typically due to [fundamental](https://bliptext.com/articles/fundamental-mode) and first [overtone](https://bliptext.com/articles/overtone) pulsation.\n[Lines](https://bliptext.com/articles/absorption-line) in the [spectrum](https://bliptext.com/articles/stellar-spectrum) of Betelgeuse show [doppler shifts](https://bliptext.com/articles/doppler-shift) indicating [radial velocity](https://bliptext.com/articles/radial-velocity) changes corresponding, very roughly, to the brightness changes.\nThis demonstrates the nature of the pulsations in size, although corresponding temperature and spectral variations are not clearly seen.\nVariations in the diameter of Betelgeuse have also been measured directly.\n[First overtone](https://bliptext.com/articles/overtone) pulsations of 185 days have been observed, and the ratio of the fundamental to overtone periods gives valuable information about the internal structure of the star and its age.\nThe source of the long secondary periods is unknown, but they cannot be explained by [radial pulsations](https://bliptext.com/articles/radial-pulsations).\nInterferometric observations of Betelgeuse have shown hotspots that are thought to be created by massive convection cells, a significant fraction of the diameter of the star and each emitting 5–10% of the total light of the star.\nOne theory to explain long secondary periods is that they are caused by the evolution of such cells combined with the rotation of the star.\nOther theories include close binary interactions, [chromospheric](https://bliptext.com/articles/chromosphere) magnetic activity influencing mass loss, or non-radial pulsations such as [g-modes](https://bliptext.com/articles/g-mode-pulsation).\nIn addition to the discrete dominant periods, small-amplitude [stochastic](https://bliptext.com/articles/stochastic) variations are seen.\nIt is proposed that this is due to [granulation](https://bliptext.com/articles/granule-solar-physics), similar to the same effect on the sun but on a much larger scale.\n# [AAVSO V-band light curve of Betelgeuse (Alpha Orionis) from Dec 1988 to Aug 2002 | upload.wikimedia.org/wikipedia/commons/b/b7/Light///curve///of///Betelgeuse.png]\n# [Orion, with Betelgeuse at its usual magnitude (left) and during the unusually deep minimum in early 2020 (right) | upload.wikimedia.org/wikipedia/commons/a/ac/Betelgeuse.jpg]\n\n## Diameter\nOn 13 December 1920, Betelgeuse became the first star outside the Solar System to have the angular size of its photosphere measured.\nAlthough interferometry was still in its infancy, the experiment proved a success.\nThe researchers, using a uniform disk model, determined that Betelgeuse had a diameter of 0.047 \", although the stellar disk was likely 17% larger due to the [limb darkening](https://bliptext.com/articles/limb-darkening), resulting in an estimate for its angular diameter of about 0.055\".\nSince then, other studies have produced angular diameters that range from 0.042 to 0.069 \". Combining these data with historical distance estimates of 180 to 815 ly yields a projected radius of the stellar disk of anywhere from 1.2 to 8.9 AU. Using the Solar System for comparison, the orbit of [Mars](https://bliptext.com/articles/solar-system) is about 1.5 AU, [Ceres](https://bliptext.com/articles/solar-system) in the [asteroid belt](https://bliptext.com/articles/asteroid-belt) 2.7 AU, [Jupiter](https://bliptext.com/articles/solar-system) 5.5 AU—so, assuming Betelgeuse occupying the place of the Sun, its photosphere might extend beyond the Jovian orbit, not quite reaching [Saturn](https://bliptext.com/articles/solar-system) at 9.5 AU.\nThe precise diameter has been hard to define for several reasons:\nThe generally reported radii of large cool stars are [Rosseland radii](https://bliptext.com/articles/rosseland-optical-depth), defined as the radius of the photosphere at a specific optical depth of two-thirds.\nThis corresponds to the radius calculated from the effective temperature and bolometric luminosity.\nThe Rosseland radius differs from directly measured radii, with corrections for [limb darkening](https://bliptext.com/articles/limb-darkening) and the observation wavelength.\nFor example, a measured angular diameter of 55.6 mas would correspond to a Rosseland mean diameter of 56.2 mas, while further corrections for the existence of surrounding dust and gas shells would give a diameter of 41.9 mas.\nTo overcome these challenges, researchers have employed various solutions.\nAstronomical interferometry, first conceived by [Hippolyte Fizeau](https://bliptext.com/articles/hippolyte-fizeau) in 1868, was the seminal concept that has enabled major improvements in modern telescopy and led to the creation of the [Michelson interferometer](https://bliptext.com/articles/michelson-interferometer) in the 1880s, and the first successful measurement of Betelgeuse.\nJust as human [depth perception](https://bliptext.com/articles/depth-perception) increases when two eyes instead of one perceive an object, Fizeau proposed the observation of stars through two [apertures](https://bliptext.com/articles/apertures) instead of one to obtain [interferences](https://bliptext.com/articles/interference-wave-propagation) that would furnish information on the star's spatial intensity distribution.\nThe science evolved quickly and multiple-aperture interferometers are now used to capture [speckled images](https://bliptext.com/articles/speckle-imaging), which are synthesized using [Fourier analysis](https://bliptext.com/articles/fourier-analysis) to produce a portrait of high resolution.\nIt was this methodology that identified the hotspots on Betelgeuse in the 1990s.\nOther technological breakthroughs include [adaptive optics](https://bliptext.com/articles/adaptive-optics), [space observatories](https://bliptext.com/articles/space-observatory) like Hipparcos, [Hubble](https://bliptext.com/articles/hubble-space-telescope) and [Spitzer](https://bliptext.com/articles/spitzer-space-telescope), and the [Astronomical Multi-BEam Recombiner (AMBER)](https://bliptext.com/articles/amber-very-large-telescope), which combines the beams of three telescopes simultaneously, allowing researchers to achieve milliarcsecond [spatial resolution](https://bliptext.com/articles/spatial-resolution).\nObservations in different regions of the electromagnetic spectrum—the visible, near-infrared ([NIR](https://bliptext.com/articles/infrared)), mid-infrared (MIR), or radio—produce very different angular measurements.\nIn 1996, Betelgeuse was shown to have a uniform disk of 56.6 mas.\nIn 2000, a [Space Sciences Laboratory](https://bliptext.com/articles/space-sciences-laboratory) team measured a diameter of 54.7 mas, ignoring any possible contribution from hotspots, which are less noticeable in the mid-infrared.\nAlso included was a theoretical allowance for limb darkening, yielding a diameter of 55.2 mas.\nThe earlier estimate equates to a radius of roughly 5.6 AU or, assuming the 2008 Harper distance of 197 pc, a figure roughly the size of the Jovian orbit of 5.5 AU.\nIn 2004, a team of astronomers working in the near-infrared announced that the more accurate photospheric measurement was 43.33 mas.\nThe study also put forth an explanation as to why varying wavelengths from the visible to mid-infrared produce different diameters: the star is seen through a thick, warm extended atmosphere.\nAt short wavelengths (the visible spectrum) the atmosphere scatters light, thus slightly increasing the star's diameter.\nAt near-infrared wavelengths ([K](https://bliptext.com/articles/k-band-infrared) and [L bands](https://bliptext.com/articles/l-band-infrared)), the scattering is negligible, so the classical photosphere can be directly seen; in the mid-infrared the scattering increases once more, causing the thermal emission of the warm atmosphere to increase the apparent diameter.\nStudies with the [IOTA](https://bliptext.com/articles/infrared-optical-telescope-array) and VLTI published in 2009 brought strong support to the idea of dust shells and a molecular shell (MOLsphere) around Betelgeuse, and yielded diameters ranging from 42.57 to 44.28 mas with comparatively insignificant margins of error.\nIn 2011, a third estimate in the near-infrared corroborating the 2009 numbers, this time showing a limb-darkened disk diameter of 42.49 mas.\nThe near-infrared photospheric diameter of 43.33 mas at the Hipparcos distance of 152 pc equates to about 3.4 AU or.\nA 2014 paper derives an angular diameter of 42.28 mas (equivalent to a 41.01 mas uniform disc) using H and K band observations made with the VLTI AMBER instrument.\nIn 2009 it was announced that the radius of Betelgeuse had shrunk from 1993 to 2009 by 15%, with the 2008 angular measurement equal to 47 mas.\nUnlike most earlier papers, this study used measurements at one specific wavelength over 15 years.\nThe diminution in Betelgeuse's [apparent size](https://bliptext.com/articles/apparent-size) equates to a range of values between 56 mas seen in 1993 to 47 mas seen in 2008—a contraction of almost 0.9 AU in 15 years.\nThe observed contraction is generally believed to be a variation in just a portion of the extended atmosphere around Betelgeuse, and observations at other wavelengths have shown an increase in diameter over a similar period.\nThe latest models of Betelgeuse adopt a photospheric angular diameter of around 43 mas, with multiple shells out to 50–60 mas.\nAssuming a distance of 197 pc, this means a stellar diameter of 887 R_solar.\nOnce considered as having the largest angular diameter of any star in the sky after the [Sun](https://bliptext.com/articles/sun), Betelgeuse lost that distinction in 1997 when a group of astronomers measured [R Doradus](https://bliptext.com/articles/r-doradus) with a diameter of 57 mas, although [R Doradus](https://bliptext.com/articles/r-doradus), being much closer to Earth at about 200 ly, has a linear diameter roughly one-third that of Betelgeuse.\n# [Size comparison between Arcturus, Rigel, S Doradus, Antares, and Betelgeuse | upload.wikimedia.org/wikipedia/commons/0/03/Arcturus///to///Betelgeuse///comparison.jpg]\n# [Size comparison of Betelgeuse, Mu Cephei, KY Cygni, and V354 Cephei, according to Emily Levesque | upload.wikimedia.org/wikipedia/commons/5/50/Mukyv354.png]\n# [Radio image from 1998 showing the size of Betelgeuse's photosphere (circle) and the effect of convective forces on the star's atmosphere | upload.wikimedia.org/wikipedia/commons/7/75/Betelgeuse///radio///wavelengths.jpg]\n# [Infrared image of Betelgeuse, Meissa and Bellatrix with surrounding nebulae | upload.wikimedia.org/wikipedia/commons/d/d4/Orion%27s///Big///Head///Revealed///in///Infrared.jpg]\n\n## Occultations\nBetelgeuse is too far from the ecliptic to be occulted by the major planets, but those by some [asteroids](https://bliptext.com/articles/asteroid) (which are more wide-ranging and much more numerous) occur frequently.\nA partial occultation by the 19th magnitude asteroid occurred on 2 January 2012.\nIt was partial because the angular diameter of the star was larger than that of the asteroid; the brightness of Betelgeuse dropped by only about 0.01 magnitudes.\nThe 14th magnitude asteroid [319 Leona](https://bliptext.com/articles/319-leona) was predicted to occult on 12 December 2023, 01:12 UTC.\nTotality was at first uncertain, and the occulation was projected to only last approximately twelve seconds (visible on a narrow path on Earth's surface, the exact width and location of which was initially uncertain due to lack of precise knowledge of the size and path of the asteroid).\nProjections were later refined as more data were analyzed for a totality (\"ring of fire\") of approximately five seconds and a 60 km wide path stretching from Tajikistan, Armenia, Turkey, Greece, Italy, Spain, the Atlantic Ocean, Miami, Florida and the [Florida Keys](https://bliptext.com/articles/florida-keys) to parts of Mexico.\n(The serendiptous event would also afford detailed observations of 319 Leona itself.) Among other programmes 80 [amateur astronomers](https://bliptext.com/articles/citizen-science) in Europe alone have been coordinated by astrophysicist [Miguel Montargès](https://bliptext.com/articles/miguel-montarg-s), et al. of the [Paris Observatory](https://bliptext.com/articles/paris-observatory) for the event.\n# [Predicted path using SOLEX | upload.wikimedia.org/wikipedia/commons/6/6a/Leona///Betelgeuse.png]\n\n# Physical characteristics\nStar-sizes.jpg and several stars, including Betelgeuse: 1. Mercury < Mars < Venus < Earth\n2. Earth < Neptune < Uranus < Saturn < Jupiter\n3. Jupiter < Wolf 359 < Sun < Sirius\n4. Sirius < Pollux < Arcturus < Aldebaran\n5. Aldebaran < Rigel < Antares < Betelgeuse\n6. Betelgeuse < Mu Cephei < VV Cephei A < VY Canis Majoris\n]]\nBetelgeuse is a very large, luminous but cool star classified as an M1-2 Ia-ab [red supergiant](https://bliptext.com/articles/red-supergiant).\nThe letter \"M\" in this designation means that it is a red star belonging to the [M spectral class](https://bliptext.com/articles/class-m-star) and therefore has a relatively low photospheric temperature; the \"Ia-ab\" suffix [luminosity class](https://bliptext.com/articles/yerkes-spectral-classification-scheme) indicates that it is an intermediate-luminosity supergiant, with properties partway between a normal supergiant and a luminous supergiant.\nSince 1943, the spectrum of Betelgeuse has served as one of the stable anchor points by which other stars are classified.\nUncertainty in the star's surface temperature, diameter, and distance make it difficult to achieve a precise measurement of Betelgeuse's luminosity, but research from 2012 quotes a luminosity of around, assuming a distance of 200 pc.\nStudies since 2001 report effective temperatures ranging from 3,250 to 3,690 [K](https://bliptext.com/articles/kelvin).\nValues outside this range have previously been reported, and much of the variation is believed to be real, due to pulsations in the atmosphere.\nThe star is also a slow rotator and the most recent velocity recorded was 5.45 km/s —much slower than [Antares](https://bliptext.com/articles/antares) which has a rotational velocity of 20 km/s.\nThe rotation period depends on Betelgeuse's size and orientation to Earth, but it has been calculated to take 36 years to turn on its axis, inclined at an angle of around 60 ° to Earth.\nIn 2004, astronomers using computer simulations speculated that even if Betelgeuse is not rotating it might exhibit large-scale magnetic activity in its extended atmosphere, a factor where even moderately strong fields could have a meaningful influence over the star's dust, wind and mass-loss properties.\nA series of [spectropolarimetric](https://bliptext.com/articles/spectropolarimetry) observations obtained in 2010 with the [Bernard Lyot Telescope](https://bliptext.com/articles/bernard-lyot-telescope) at [Pic du Midi Observatory](https://bliptext.com/articles/pic-du-midi-observatory) revealed the presence of a weak magnetic field at the surface of Betelgeuse, suggesting that the giant convective motions of supergiant stars are able to trigger the onset of a small-scale [dynamo effect](https://bliptext.com/articles/dynamo-effect).\n\n## Mass\nBetelgeuse has no known orbital companions, so its mass cannot be calculated by that direct method.\nModern mass estimates from theoretical modelling have produced values of, with values of – from older studies.\nIt has been calculated that Betelgeuse began its life as a star of, based on a solar luminosity of 90,000–150,000.\nA novel method of determining the supergiant's mass was proposed in 2011, arguing for a current stellar mass of with an upper limit of 16.6 and lower of, based on observations of the star's intensity profile from narrow H-band interferometry and using a photospheric measurement of roughly 4.3 AU or.\nA probablystic age prior analysis give a current mass of and an initial mass of.\nBetelgeuse's mass can also be estimated based on its position on the [colormagnitudediagram (CMD)](https://bliptext.com/articles/hertzsprung-russell-diagram).\nBetelgeuse's color may have changed from yellow (or possibly orange; i.e. a yellow supergiant) to red in the last few thousand years, based on a 2022 review of historical records.\nThis color change combined with the CMD suggest a mass of and age of 14 Myr, and a distance from 125 to 150 parsecs (~400 to 500 light years).\n\n## Motion\nThe [kinematics](https://bliptext.com/articles/kinematics) of Betelgeuse are complex.\nThe age of Class M supergiants with an initial mass of is roughly 10 million years.\nStarting from its present position and motion, a projection back in time would place Betelgeuse around 290 parsecs farther from the [galactic plane](https://bliptext.com/articles/galactic-plane)—an implausible location, as there is no [star formation](https://bliptext.com/articles/star-formation) [region](https://bliptext.com/articles/molecular-cloud) there.\nMoreover, Betelgeuse's projected pathway does not appear to intersect with the [25 Ori](https://bliptext.com/articles/25-orionis) [subassociation](https://bliptext.com/articles/orion-ob1-association) or the far younger Orion Nebula Cluster (ONC, also known as Ori OB1d), particularly since [Very Long Baseline Array](https://bliptext.com/articles/very-long-baseline-array) astrometry yields a distance from Betelgeuse to the ONC of between 389 and 414 parsecs.\nConsequently, it is likely that Betelgeuse has not always had its current motion through space but has changed course at one time or another, possibly the result of a nearby [stellar explosion](https://bliptext.com/articles/supernova).\nAn observation by the [Herschel Space Observatory](https://bliptext.com/articles/herschel-space-observatory) in January 2013 revealed that the star's winds are crashing against the surrounding interstellar medium.\nThe most likely star-formation scenario for Betelgeuse is that it is a runaway star from the [Orion OB1 association](https://bliptext.com/articles/orion-ob1-association).\nOriginally a member of a high-mass multiple system within Ori OB1a, Betelgeuse was probably formed about 10–12 million years ago, but has evolved rapidly due to its high mass.\nH. Bouy and J. Alves suggested in 2015 that Betelgeuse may instead be a member of the newly discovered Taurion [OB association](https://bliptext.com/articles/ob-association).\n# [Map showing the Orion OB1 association, which contains the blue supergiants of Orion's Belt and the Orion Nebula. Betelgeuse is believed to be a runaway star that was ejected from the Orion OB1 association. | upload.wikimedia.org/wikipedia/commons/4/48/Orion///OB1///%26///25///Ori///Group.png]\n\n## Circumstellar dynamics\nIn the late phase of [stellar evolution](https://bliptext.com/articles/stellar-evolution), massive stars like Betelgeuse exhibit high rates of [mass loss](https://bliptext.com/articles/stellar-mass-loss), possibly as much as every 10,000 years, resulting in a complex [circumstellar environment](https://bliptext.com/articles/circumstellar-envelope) that is constantly in flux.\nIn a 2009 paper, stellar mass loss was cited as the \"key to understanding the evolution of the universe from the earliest cosmological times to the current epoch, and of planet formation and the formation of life itself\".\nHowever, the physical mechanism is not well understood.\nWhen [Martin Schwarzschild](https://bliptext.com/articles/martin-schwarzschild) first proposed his theory of huge convection cells, he argued it was the likely cause of mass loss in evolved supergiants like Betelgeuse.\nRecent work has corroborated this hypothesis, yet there are still uncertainties about the structure of their convection, the mechanism of their mass loss, the way dust forms in their extended atmosphere, and the conditions which precipitate their dramatic finale as a type II supernova.\nIn 2001, Graham Harper estimated a stellar wind at every 10,000 years, but research since 2009 has provided evidence of episodic mass loss making any total figure for Betelgeuse uncertain.\nCurrent observations suggest that a star like Betelgeuse may spend a portion of its lifetime as a [red supergiant](https://bliptext.com/articles/red-supergiant-star), but then cross back across the H–R diagram, pass once again through a brief [yellow supergiant](https://bliptext.com/articles/yellow-supergiant-star) phase and then explode as a [blue supergiant](https://bliptext.com/articles/blue-supergiant) or [Wolf–Rayet star](https://bliptext.com/articles/wolf-rayet-star).\nAstronomers may be close to solving this mystery.\nThey noticed a large plume of gas extending at least six times its stellar radius indicating that Betelgeuse is not shedding matter evenly in all directions.\nThe plume's presence implies that the spherical symmetry of the star's photosphere, often observed in the infrared, is not preserved in its close environment.\nAsymmetries on the stellar disk had been reported at different wavelengths.\nHowever, due to the refined capabilities of the [NACO](https://bliptext.com/articles/list-of-instruments-at-the-very-large-telescope) adaptive optics on the VLT, these asymmetries have come into focus.\nThe two mechanisms that could cause such asymmetrical mass loss, were large-scale convection cells or polar mass loss, possibly due to rotation.\nProbing deeper with ESO's AMBER, gas in the supergiant's extended atmosphere has been observed vigorously moving up and down, creating bubbles as large as the supergiant itself, leading his team to conclude that such stellar upheaval is behind the massive plume ejection observed by Kervella.\n# [Image from ESO's Very Large Telescope showing the stellar disk and an extended atmosphere with a previously unknown plume of surrounding gas | upload.wikimedia.org/wikipedia/commons/9/92/ESO-Betelgeuse.jpg]\n# [Artist's rendering from ESO showing Betelgeuse with a gigantic bubble boiling on its surface and a radiant plume of gas being ejected to six photospheric radii or roughly the orbit of Neptune | upload.wikimedia.org/wikipedia/commons/8/81/Betelgeuse///Plume///eso0927d.jpg]\n\n### Asymmetric shells\nIn addition to the photosphere, six other components of Betelgeuse's atmosphere have now been identified.\nThey are a molecular environment otherwise known as the MOLsphere, a gaseous envelope, a chromosphere, a dust environment and two outer shells (S1 and S2) composed of [carbon monoxide](https://bliptext.com/articles/carbon-monoxide) (CO).\nSome of these elements are known to be asymmetric while others overlap.\nAt about 0.45 stellar radii (~2–3 AU) above the photosphere, there may lie a molecular layer known as the MOLsphere or molecular environment.\nStudies show it to be composed of water vapor and carbon monoxide with an effective temperature of about 1,500 K. Water vapor had been originally detected in the supergiant's spectrum in the 1960s with the two Stratoscope projects but had been ignored for decades.\nThe MOLsphere may also contain [SiO](https://bliptext.com/articles/silicon-monoxide) and [Al2O3](https://bliptext.com/articles/aluminium-oxide)—molecules which could explain the formation of dust particles.\nAnother cooler region, the asymmetric gaseous envelope, extends for several radii (~10–40 AU) from the photosphere.\nIt is enriched in oxygen and especially in [nitrogen](https://bliptext.com/articles/nitrogen) relative to carbon.\nThese composition anomalies are likely caused by contamination by [CNO](https://bliptext.com/articles/cno-cycle)-processed material from the inside of Betelgeuse.\nRadio-telescope images taken in 1998 confirm that Betelgeuse has a highly complex atmosphere, with a temperature of 3,450 K, similar to that recorded on the star's surface but much lower than surrounding gas in the same region.\nThe VLA images also show this lower-temperature gas progressively cools as it extends outward.\nAlthough unexpected, it turns out to be the most abundant constituent of Betelgeuse's atmosphere.\n\"This alters our basic understanding of red-supergiant star atmospheres\", explained Jeremy Lim, the team's leader.\n\"Instead of the star's atmosphere expanding uniformly due to gas heated to high temperatures near its surface, it now appears that several giant convection cells propel gas from the star's surface into its atmosphere.\"\nThis is the same region in which Kervella's 2009 finding of a bright plume, possibly containing carbon and nitrogen and extending at least six photospheric radii in the southwest direction of the star, is believed to exist.\nThe [chromosphere](https://bliptext.com/articles/chromosphere) was directly imaged by the Faint Object Camera on board the Hubble Space Telescope in ultraviolet wavelengths.\nThe images also revealed a bright area in the southwest quadrant of the disk.\nThe average radius of the chromosphere in 1996 was about 2.2 times the optical disk (~10 AU) and was reported to have a temperature no higher than 5,500 K. However, in 2004 observations with the STIS, Hubble's high-precision spectrometer, pointed to the existence of warm chromospheric plasma at least one arcsecond away from the star.\nAt a distance of 197 pc, the size of the chromosphere could be up to 200 AU.\nThe observations have conclusively demonstrated that the warm chromospheric plasma spatially overlaps and co-exists with cool gas in Betelgeuse's gaseous envelope as well as with the dust in its circumstellar dust shells.\nThe first claim of a dust shell surrounding Betelgeuse was put forth in 1977 when it was noted that dust shells around mature stars often emit large amounts of radiation in excess of the photospheric contribution.\nUsing [heterodyne interferometry](https://bliptext.com/articles/interferometry), it was concluded that the red supergiant emits most of its excess radiation from positions beyond 12 stellar radii or roughly the distance of the [Kuiper belt](https://bliptext.com/articles/kuiper-belt) at 50 to 60 AU, which depends on the assumed stellar radius.\nSince then, there have been studies done of this dust envelope at varying wavelengths yielding decidedly different results.\nStudies from the 1990s have estimated the inner radius of the dust shell anywhere from 0.5 to 1 arcseconds, or 100 to 200 AU.\nThese studies point out that the dust environment surrounding Betelgeuse is not static.\nIn 1994, it was reported that Betelgeuse undergoes sporadic decades-long dust production, followed by inactivity.\nIn 1997, significant changes in the dust shell's morphology in one year were noted, suggesting that the shell is asymmetrically illuminated by a stellar radiation field strongly affected by the existence of photospheric hotspots.\nThe 1984 report of a giant asymmetric dust shell 1 pc (206,265 AU) has not been corroborated by recent studies, although another published the same year said that three dust shells were found extending four light-years from one side of the decaying star, suggesting that Betelgeuse sheds its outer layers as it moves.\nAlthough the exact size of the two outer [CO](https://bliptext.com/articles/carbon-monoxide) shells remains elusive, preliminary estimates suggest that one shell extends from about 1.5 to 4.0 [arcseconds](https://bliptext.com/articles/arcseconds) and the other expands as far as 7.0 [arcseconds](https://bliptext.com/articles/arcseconds).\nAssuming the Jovian orbit of 5.5 AU as the star radius, the inner shell would extend roughly 50 to 150 stellar radii (~300 to 800 AU) with the outer one as far as 250 stellar radii (~1,400 AU).\nThe Sun's [heliopause](https://bliptext.com/articles/heliopause-astronomy) is estimated at 100 AU, so the size of this outer shell would be almost fourteen times the size of the Solar System.\n# [Exterior view of ESO's Very Large Telescope (VLT) in Paranal, Chile | upload.wikimedia.org/wikipedia/commons/4/4b/ESO///Paranal///Platform.jpg]\n# [Interior view of one of the four 8.2-meter Unit Telescopes at ESO's VLT | upload.wikimedia.org/wikipedia/commons/9/97/Eso-paranal-16.jpg]\n# [This infrared image from the ESO's VLT shows complex shells of gas and dust around Betelgeuse – the tiny red circle in the middle is the size of the photosphere. | upload.wikimedia.org/wikipedia/commons/a/a0/Nebula///around///Betelgeuse.jpg]\n\n### Supersonic bow shock\nBetelgeuse is travelling through the interstellar medium at a speed of 30 km/second (i.e. ~6.3 AU/year) creating a [bow shock](https://bliptext.com/articles/bow-shocks-in-astrophysics).\nThe shock is not created by the star, but by its powerful [stellar wind](https://bliptext.com/articles/stellar-wind) as it ejects vast amounts of gas into the interstellar medium at a speed of 17 km/s, heating the material surrounding the star, thereby making it visible in infrared light.\nBecause Betelgeuse is so bright, it was only in 1997 that the bow shock was first imaged.\nThe [cometary](https://bliptext.com/articles/comet) structure is estimated to be at least one parsec wide, assuming a distance of 643 light-years.\n[Hydrodynamic](https://bliptext.com/articles/fluid-dynamics) simulations of the bow shock made in 2012 indicate that it is very young—less than 30,000 years old—suggesting two possibilities: that Betelgeuse moved into a region of the interstellar medium with different properties only recently or that Betelgeuse has undergone a significant transformation producing a changed stellar wind.\nA 2012 paper, proposed that this phenomenon was caused by Betelgeuse transitioning from a [blue supergiant](https://bliptext.com/articles/blue-supergiant) (BSG) to a red supergiant (RSG).\nThere is evidence that in the late evolutionary stage of a star like Betelgeuse, such stars \"may undergo rapid transitions from red to blue and vice versa on the Hertzsprung–Russell diagram, with accompanying rapid changes to their stellar winds and bow shocks.\"\nMoreover, if future research bears out this hypothesis, Betelgeuse may prove to have traveled close to 200,000 AU as a red supergiant scattering as much as 3 M_solar along its trajectory.\n\n# Life phases\nBetelgeuse is a red supergiant that has evolved from an [O-type main-sequence star](https://bliptext.com/articles/o-type-main-sequence-star).\nAfter core hydrogen exhaustion, Betelgeuse evolved into a blue supergiant before evolving into its current red supergiant form.\nIts core will eventually collapse, producing a [supernova](https://bliptext.com/articles/supernova) explosion and leaving behind a compact [remnant](https://bliptext.com/articles/supernova-remnant).\nThe details depend on the exact initial mass and other physical properties of that main sequence star.\n\n## Main sequence\nThe initial mass of Betelgeuse can only be estimated by testing different stellar evolutionary models to match its current observed properties.\nThe unknowns of both the models and the current properties mean that there is considerable uncertainty in Betelgeuse's initial appearance, but its mass is usually estimated to have been in the range of, with modern models finding values of.\nIts chemical makeup can be reasonably assumed to have been around 70% hydrogen, 28% helium, and 2.4% heavy elements, slightly more metal-rich than the Sun but otherwise similar.\nThe initial rotation rate is more uncertain, but models with slow to moderate initial rotation rates produce the best matches to Betelgeuse's current properties.\nThat main sequence version of Betelgeuse would have been a hot luminous star with a spectral type such as O9V.\nA star would take between 11.5 and 15 million years to reach the red supergiant stage, with more rapidly-rotating stars taking the longest.\nRapidly-rotating stars take 9.3 million years to reach the red supergiant stage, while stars with slow rotation take only 8.1 million years.\nThese are the best estimates of Betelgeuse's current age, as the time since its [zero age main sequence](https://bliptext.com/articles/main-sequence) stage is estimated to be 8.0–8.5 million years as a star with no rotation.\n# [Hertzsprung–Russell diagram identifying supergiants like Betelgeuse that have moved off the main sequence | upload.wikimedia.org/wikipedia/commons/9/96/Hertzsprung-Russell///Diagram///-///ESO.png]\n\n## After core hydrogen exhaustion\nBetelgeuse's time spent as a red supergiant can be estimated by comparing mass loss rates to the observed circumstellar material, as well as the abundances of heavy elements at the surface.\nEstimates range from 10,000 years to a maximum of 140,000 years.\nBetelgeuse appears to undergo short periods of heavy mass loss and is a runaway star moving rapidly through space, so comparisons of its current mass loss to the total lost mass are difficult.\nThe surface of Betelgeuse shows enhancement of nitrogen, relatively low levels of carbon, and a high proportion of [13C](https://bliptext.com/articles/carbon-13) relative to [12C](https://bliptext.com/articles/carbon-12), all indicative of a star that has experienced the [first dredge-up](https://bliptext.com/articles/dredge-up).\nHowever, the first dredge-up occurs soon after a star reaches the red supergiant phase and so this only means that Betelgeuse has been a red supergiant for at least a few thousand years.\nThe best prediction is that Betelgeuse has already spent around 40,000 years as a red supergiant, having left the main sequence perhaps one million years ago.\nThe current mass can be estimated from evolutionary models from the initial mass and the expected mass lost so far.\nFor Betelgeuse, the total mass lost is predicted to be no more than about, giving a current mass of , considerably higher than estimated by other means such as pulsational properties or limb-darkening models.\nAll stars more massive than about are expected to end their lives when their cores collapse, typically producing a supernova explosion.\nUp to about, a type II-P supernova is always produced from the red supergiant stage.\nMore massive stars can lose mass quickly enough that they evolve towards higher temperatures before their cores can collapse, particularly for rotating stars and models with especially high mass loss rates.\nThese stars can produce type II-L or type IIb supernovae from yellow or blue supergiants, or type I b/c supernovae from Wolf–Rayet stars.\nModels of rotating stars predict a peculiar type II supernova similar to [SN 1987A](https://bliptext.com/articles/sn-1987a) from a [blue supergiant](https://bliptext.com/articles/blue-supergiant) progenitor.\nOn the other hand, non-rotating models predict a type II-P supernova from a red [supergiant](https://bliptext.com/articles/supergiant) progenitor.\nThe time until Betelgeuse explodes depends on the predicted initial conditions and on the estimate of the time already spent as a red supergiant.\nThe total lifetime from the start of the red supergiant phase to core collapse varies from about 300,000 years for a rotating star, 550,000 years for a rotating star, and up to a million years for a non-rotating star.\nGiven the estimated time since Betelgeuse became a red supergiant, estimates of its remaining lifetime range from a \"best guess\" of under 100,000 years for a non-rotating model to far longer for rotating models or lower-mass stars.\nBetelgeuse's suspected birthplace in the [Orion OB1 association](https://bliptext.com/articles/orion-ob1-association) is the location of several previous supernovae.\nIt is believed that runaway stars may be caused by supernovae, and there is strong evidence that [OB stars](https://bliptext.com/articles/ob-star) [μ Columbae](https://bliptext.com/articles/mu-columbae), [AE Aurigae](https://bliptext.com/articles/ae-aurigae), and [53 Arietis](https://bliptext.com/articles/53-arietis) all originated from such explosions in Ori OB1 2.2, 2.7, and 4.9 million years ago.\nA typical type II-P [supernova](https://bliptext.com/articles/supernova) emits 2 J of [neutrinos](https://bliptext.com/articles/neutrino) and produces an explosion with a kinetic energy of 2 J. As seen from Earth, Betelgeuse as a type IIP [supernova](https://bliptext.com/articles/supernova) would have a peak apparent magnitude somewhere in the range −8 to −12.\nThis would be easily visible in daylight, with a possible brightness up to a significant fraction of the [full moon](https://bliptext.com/articles/full-moon), though likely not exceeding it.\nThis type of supernova would remain at roughly constant brightness for 2–3 months before rapidly dimming.\nThe visible light is produced mainly by the radioactive decay of [cobalt](https://bliptext.com/articles/cobalt), and sustains its brightness due to the increasing transparency of the cooling hydrogen ejected by the supernova.\n# [This is what Betelgeuse may have looked like up until about 1 million years ago, when it was a main-sequence star. | upload.wikimedia.org/wikipedia/commons/f/fc/O-type///star.png]\n# [Celestia depiction of Orion as it might appear from Earth when Betelgeuse explodes as a supernova, which could be brighter than the supernova that exploded in 1006 (SN 1006) | upload.wikimedia.org/wikipedia/commons/5/57/Betelgeuse///supernova.png]\n\n### Media reporting\nDue to misunderstandings caused by the 2009 publication of the star's 15% contraction, apparently of its outer atmosphere, Betelgeuse has frequently been the subject of scare stories and rumors suggesting that it will explode within a year, and leading to exaggerated claims about the consequences of such an event.\nThe timing and prevalence of these rumors have been linked to broader misconceptions of astronomy, particularly to doomsday predictions relating to the [Mayan calendrical apocalypse](https://bliptext.com/articles/2012-phenomenon).\nBetelgeuse is not likely to produce a [gamma-ray burst](https://bliptext.com/articles/gamma-ray-burst) and is not close enough for its [X-rays](https://bliptext.com/articles/x-ray), ultraviolet radiation, or ejected material to cause significant effects on [Earth](https://bliptext.com/articles/earth).\nFollowing the dimming of Betelgeuse in December 2019, reports appeared in the science and mainstream media that again included speculation that the star might be about to explode as a supernova – even in the face of scientific research that a supernova is not expected for perhaps 100,000 years.\nSome outlets reported the magnitude as faint as +1.3 as an unusual and interesting phenomenon, like Astronomy magazine, the [National Geographic](https://bliptext.com/articles/national-geographic), and the Smithsonian.\nSome mainstream media, like [The Washington Post](https://bliptext.com/articles/the-washington-post), [ABC News](https://bliptext.com/articles/abc-news-australia) in Australia, and [Popular Science](https://bliptext.com/articles/popular-science), reported that a supernova was possible but unlikely, whilst other outlets falsely portrayed a supernova as an imminent realistic possibility.\n[CNN](https://bliptext.com/articles/cnn), for example, chose the headline \"A giant red star is acting weird and scientists think it may be about to explode\", while the [New York Post](https://bliptext.com/articles/new-york-post) declared Betelgeuse as \"due for explosive supernova\".\n[Phil Plait](https://bliptext.com/articles/phil-plait), in his [Bad Astronomy](https://bliptext.com/articles/bad-astronomy) blog, noting that Betelgeuse's recent behaviour, \"[w]hile unusual . . . isn't unprecedented,\" argued that the star is not likely to explode \"for a long, long time.\"\n[Dennis Overbye](https://bliptext.com/articles/dennis-overbye) of [The New York Times](https://bliptext.com/articles/the-new-york-times) agreed that an explosion was not imminent but added that \"astronomers are having fun thinking about it.\"\nFollowing the eventual supernova, [a small dense remnant](https://bliptext.com/articles/compact-star) will be left behind, either a [neutron star](https://bliptext.com/articles/neutron-star) or [black hole](https://bliptext.com/articles/black-hole).\nBetelgeuse does not seem to have a core massive enough for a black hole, so the remnant will probably be a neutron star of approximately.\n\n# Ethnological attributes\n\n## Spelling and pronunciation\nBetelgeuse has also been spelled Betelgeux and, in [German](https://bliptext.com/articles/german-language), Beteigeuze (according to [Bode](https://bliptext.com/articles/johann-elert-bode)).\nBetelgeux and Betelgeuze were used until the early 20th century, when the spelling Betelgeuse became universal.\nConsensus on its pronunciation is weak and is as varied as its spellings:\nThe -urz pronunciations are attempts to render the French eu sound; they only work in r-dropping accents.\n\n## Etymology\nBetelgeuse is often mistranslated as \"armpit of the central one\".\nIn his 1899 work [Star-Names and Their Meanings](https://bliptext.com/articles/star-names), American amateur naturalist Richard Hinckley Allen stated the derivation was from the ابط الجوزاء , which he claimed degenerated into a number of forms, including Bed Elgueze, Beit Algueze, Bet El-gueze, and Beteigeuze, to the forms Betelgeuse, Betelguese, Betelgueze and Betelgeux.\nThe star was named Beldengeuze in the [Alfonsine Tables](https://bliptext.com/articles/alfonsine-tables), and Italian [Jesuit](https://bliptext.com/articles/jesuit) priest and astronomer [Giovanni Battista Riccioli](https://bliptext.com/articles/giovanni-battista-riccioli) had called it Bectelgeuze or Bedalgeuze.\nPaul Kunitzsch, Professor of Arabic Studies at the University of Munich, refuted Allen's derivation and instead proposed that the full name is a corruption of the Arabic يد الجوزاء , meaning \"the Hand of al-Jauzā '\" ; i.e., Orion.\nEuropean mistransliteration into [medieval Latin](https://bliptext.com/articles/medieval-latin) led to the first character y (**ﻴ**, with two dots underneath) being misread as a b (**ﺒ**, with only one dot underneath).\nDuring the [Renaissance](https://bliptext.com/articles/renaissance), the star's name was written as بيت الجوزاء **' (\"house of Orion\") or بط الجوزاء '**, incorrectly thought to mean \"armpit of Orion\" (a true translation of \"armpit\" would be ابط, transliterated as ).\nThis led to the modern rendering as Betelgeuse.\nOther writers have since accepted Kunitzsch's explanation.\nThe last part of the name, \"-elgeuse\", comes from the Arabic الجوزاء , a historical Arabic name of the constellation [Orion](https://bliptext.com/articles/orion-constellation), a feminine name in old [Arabian legend](https://bliptext.com/articles/arabian-legend), and of uncertain meaning.\nBecause جوز **', the [root](https://bliptext.com/articles/root-linguistics) of '**, means \"middle\", roughly means \"the Central One\".\nThe modern Arabic name for Orion is الجبار **' (\"the Giant\"), although the use of الجوزاء '** in the star's name has continued.\nThe 17th-century English translator [Edmund Chilmead](https://bliptext.com/articles/edmund-chilmead) gave it the name Ied Algeuze (\"Orion's Hand\"), from [Christmannus](https://bliptext.com/articles/jakob-christmann).\nOther Arabic names recorded include اليد اليمنى **' (\"the Right Hand\"), الذراع '** (\"the Arm\"), and المنكب **' (\"the Shoulder\"), all of al-Jauzā, Orion, as منكب الجوزاء '**.\n# [An illustration of Orion (horizontally reversed) in al-Sufi's Book of Fixed Stars. Betelgeuze is annotated as Yad al-Jauzā (\"Hand of Orion\"), one of the proposed etymological origins of its modern name, and also as Mankib al Jauzā' (\"Shoulder of Orion\"). | upload.wikimedia.org/wikipedia/commons/b/bd/Al-Sufi%27s///Orion%2C///1125///Baghdad///copy%2C///Doha///Museum///of///Islamic///Art///Ms///2.///1998.///SO.jpg]\n# [Dunhuang Star Chart, circa AD 700, showing 參宿四 Shēnxiùsì (Betelgeuse), the Fourth Star of the constellation of Three Stars | upload.wikimedia.org/wikipedia/commons/9/95/Dunhuang///Star///Atlas///-///Orion.jpg]\n\n## Other names\nOther names for Betelgeuse included the Persian Bašn \"the Arm\", and [Coptic](https://bliptext.com/articles/coptic-language) Klaria \"an Armlet\".\nBahu was its [Sanskrit](https://bliptext.com/articles/sanskrit) name, as part of a Hindu understanding of the constellation as a running antelope or stag.\nIn traditional [Chinese astronomy](https://bliptext.com/articles/chinese-astronomy), the [name](https://bliptext.com/articles/chinese-star-names) for Betelgeuse is 参宿四 (Shēnxiùsì, the Fourth Star of the constellation of [Three Stars](https://bliptext.com/articles/three-stars-chinese-constellation)) as the [Chinese constellation](https://bliptext.com/articles/orion-in-chinese-astronomy) 参宿 originally referred to the three stars in [Orion's Belt](https://bliptext.com/articles/orion-s-belt).\nThis constellation was ultimately expanded to ten stars, but the earlier name stuck.\nIn Japan, the [Taira, or Heike, clan](https://bliptext.com/articles/heike-clan) adopted Betelgeuse and its red color as its symbol, calling the star Heike-boshi, (平家星), while the [Minamoto, or Genji, clan](https://bliptext.com/articles/minamoto-clan) chose Rigel and its white color.\nThe two powerful families fought a [legendary war](https://bliptext.com/articles/genpei-war) in Japanese history, the stars seen as facing each other off and only kept apart by the Belt.\nIn Tahitian lore, Betelgeuse was one of the pillars propping up the sky, known as Anâ-varu, the pillar to sit by.\nIt was also called Ta'urua-nui-o-Mere \"Great festivity in parental yearnings\".\nA Hawaiian term for it was Kaulua-koko (\"brilliant red star\").\nThe [Lacandon people](https://bliptext.com/articles/lacandon-people) of Central America knew it as chäk tulix (\"red butterfly\").\nAstronomy writer [Robert Burnham Jr.](https://bliptext.com/articles/robert-burnham-jr) proposed the term padparadaschah, which denotes a rare orange sapphire in India, for the star.\n\n## Mythology\nWith the [history of astronomy](https://bliptext.com/articles/history-of-astronomy) intimately associated with mythology and astrology before the [scientific revolution](https://bliptext.com/articles/scientific-revolution), the red star, like the planet Mars that derives its name from a [Roman war god](https://bliptext.com/articles/mars-mythology), has been closely associated with the martial [archetype](https://bliptext.com/articles/archetype) of conquest for millennia, and by extension, the motif of death and rebirth.\nOther cultures have produced different myths.\nStephen R. Wilk has proposed the constellation of Orion could have represented the Greek mythological figure [Pelops](https://bliptext.com/articles/pelops), who had an artificial shoulder of ivory made for him, with Betelgeuse as the shoulder, its color reminiscent of the reddish yellow sheen of ivory.\n[Aboriginal](https://bliptext.com/articles/australian-aborigines) people from the [Great Victoria Desert](https://bliptext.com/articles/great-victoria-desert) of South Australia incorporated Betelgeuse into their oral traditions as the club of Nyeeruna (Orion), which fills with fire-magic and dissipates before returning.\nThis has been interpreted as showing that early Aboriginal observers were aware of the brightness variations of Betelgeuse.\nThe [Wardaman people](https://bliptext.com/articles/wardaman-people) of northern Australia knew the star as Ya-jungin (\"Owl Eyes Flicking\"), its variable light signifying its intermittent watching of ceremonies led by the Red Kangaroo Leader Rigel.\nIn South African mythology, Betelgeuse was perceived as a lion casting a predatory gaze toward the three zebras represented by Orion's Belt.\nIn the Americas, Betelgeuse signifies a severed limb of a man-figure (Orion)—the [Taulipang](https://bliptext.com/articles/pemon-people) of Brazil know the constellation as Zililkawai, a hero whose leg was cut off by his wife, with the variable light of Betelgeuse linked to the severing of the limb.\nSimilarly, the [Lakota people](https://bliptext.com/articles/lakota-people) of North America see it as a chief whose arm has been severed.\nA Sanskrit name for Betelgeuse is ārdrā (\"the moist one\"), eponymous of the [Ardra](https://bliptext.com/articles/ardra-nakshatra) [lunar mansion](https://bliptext.com/articles/nakshatra) in [Hindu astrology](https://bliptext.com/articles/hindu-astrology).\nThe [Rigvedic God](https://bliptext.com/articles/rigvedic-deities) of storms [Rudra](https://bliptext.com/articles/rudra) presided over the star; this association was linked by 19th-century star enthusiast [Richard Hinckley Allen](https://bliptext.com/articles/star-names-their-lore-and-meaning) to Orion's stormy nature.\nThe constellations in Macedonian folklore represented agricultural items and animals, reflecting their way of life.\nTo them, Betelgeuse was Orach (\"the ploughman\"), alongside the rest of Orion, which depicted a plough with oxen.\nThe rising of Betelgeuse at around 3 a.m. in late summer and autumn signified the time for village men to go to the fields and plough.\nTo the [Inuit](https://bliptext.com/articles/inuit-astronomy), the appearance of Betelgeuse and [Bellatrix](https://bliptext.com/articles/bellatrix) high in the southern sky after sunset marked the beginning of spring and lengthening days in late February and early March.\nThe two stars were known as Akuttujuuk (\"those [two] placed far apart\"), referring to the distance between them, mainly to people from North Baffin Island and Melville Peninsula.\nThe opposed locations of Orion and [Scorpius](https://bliptext.com/articles/scorpius), with their corresponding bright red variable stars Betelgeuse and [Antares](https://bliptext.com/articles/antares), were noted by ancient cultures around the world.\nThe setting of Orion and rising of Scorpius signify the death of Orion by the scorpion.\nIn China they signify brothers and rivals Shen and Shang.\nThe [Batak](https://bliptext.com/articles/batak-indonesia) of Sumatra marked their New Year with the first [new moon](https://bliptext.com/articles/new-moon) after the sinking of Orion's Belt below the horizon, at which point Betelgeuse remained \"like the tail of a rooster\".\nThe positions of Betelgeuse and Antares at opposite ends of the celestial sky were considered significant, and their constellations were seen as a pair of scorpions.\nScorpion days marked as nights that both constellations could be seen.\n\n## In popular culture\nAs one of the brightest and best-known stars, Betelgeuse has featured in many works of fiction.\nThe star's unusual name inspired the title of the 1988 film [Beetlejuice](https://bliptext.com/articles/beetlejuice), referring to its titular antagonist, and script writer [Michael McDowell](https://bliptext.com/articles/michael-mcdowell-author) was impressed by how many people made the connection.\nIn the popular science fiction series [The Hitchhiker's Guide to the Galaxy](https://bliptext.com/articles/the-hitchhiker-s-guide-to-the-galaxy) by [Douglas Adams](https://bliptext.com/articles/douglas-adams), [Ford Prefect](https://bliptext.com/articles/ford-prefect-character) was from \"a small planet somewhere in the vicinity of Betelgeuse.\"\nTwo American navy ships were named after the star, both of them World War II vessels, the USS Betelgeuse (AKA-11) launched in 1939 and USS Betelgeuse (AK-260) launched in 1944.\nIn 1979, the French supertanker [Betelgeuse](https://bliptext.com/articles/whiddy-island-disaster) was moored off [Whiddy Island](https://bliptext.com/articles/whiddy-island), discharging oil when it exploded, killing 50 people in one of the worst disasters in Ireland's history.\nThe [Dave Matthews Band](https://bliptext.com/articles/dave-matthews-band) song \"[Black and Blue Bird](https://bliptext.com/articles/black-and-blue-bird-song)\" references the star.\nThe [Blur](https://bliptext.com/articles/blur-band) song \"Far Out\" from their 1994 album [Parklife](https://bliptext.com/articles/parklife) mentions Betelgeuse in its lyrics.\nThe [Philip Larkin](https://bliptext.com/articles/philip-larkin) poem \"The North Ship\", found in [the collection of the same name](https://bliptext.com/articles/the-north-ship), references the star in the section \"Above 80° N\", which reads: \" 'A woman has ten claws,' / Sang the drunken boatswain; / Farther than Betelgeuse, / More brilliant than Orion / Or the planets Venus and Mars, / The star flames on the ocean; / 'A woman has ten claws,' / Sang the drunken boatswain.\"\n[Humbert Wolfe](https://bliptext.com/articles/humbert-wolfe) wrote a poem about Betelgeuse, which was set to music by [Gustav Holst](https://bliptext.com/articles/gustav-holst).\n\n# Table of angular diameter estimates\nThis table provides a non-exhaustive list of angular measurements conducted since 1920.\nAlso included is a column providing a current range of radii for each study based on Betelgeuse's most recent distance estimate (Harper et al.) of 197 pc.","wordIndex":92,"createdAt":"2025-03-21T17:57:13.702Z","user":{"id":"9N5ZIb7MxHQAFISSgadBc5qmfxfp48GB","name":"LittleCadmium","image":"https://cdn.discordapp.com/embed/avatars/5.png"}}],"article":{"id":"349b0966-970b-4b66-806e-c4d912da0459","title":"Betelgeuse","slug":"betelgeuse","content":":::summary\n:::\n\n# \n**Betelgeuse** is a [red supergiant](https://bliptext.com/articles/red-supergiant) star in the [constellation](https://bliptext.com/articles/constellation) of [Orion](https://bliptext.com/articles/orion-constellation).\nIt is usually the [tenth-brightest](https://bliptext.com/articles/list-of-brightest-[star](https://bliptext.com/articles/star)s) [star](https://bliptext.com/articles/star) in the [night sky](https://bliptext.com/articles/night-sky) and, after [Rigel](https://bliptext.com/articles/rigel), the second-brightest in its constellation.\nIt is a distinctly reddish, [semiregular variable star](https://bliptext.com/articles/semiregular-variable-star) whose [apparent magnitude](https://bliptext.com/articles/apparent-magnitude), varying between +0.0 and +1.6, has the widest range displayed by any [first-magnitude star](https://bliptext.com/articles/first-magnitude-star).\nBetelgeuse is the brightest star in the night sky at [near-infrared](https://bliptext.com/articles/near-infrared) wavelengths.\nIts [Bayer designation](https://bliptext.com/articles/bayer-designation) is ****α Ori**onis**, [Latinised](https://bliptext.com/articles/latinisation-of-names) to ****Alpha Ori**onis** and abbreviated **Alpha Ori** or **α Ori**.\nWith a radius between 640 and 764 times that of the Soup if it were at the center of our [Solar System](https://bliptext.com/articles/solar-system), its surface would lie beyond the [asteroid belt](https://bliptext.com/articles/asteroid-belt) and it would engulf the [orbits](https://bliptext.com/articles/orbit) of [Mercury](https://bliptext.com/articles/mercury-planet), [Venus](https://bliptext.com/articles/venus), [Earth](https://bliptext.com/articles/earth), and [Mars](https://bliptext.com/articles/mars).\nCalculations of Betelgeuse's mass range from slightly under ten to a little over twenty times that of the [Sun](https://bliptext.com/articles/sun).\nFor [various reasons](https://bliptext.com/articles/), its distance has been quite difficult to measure; current best estimates are of the order of 400–600 [light-years](https://bliptext.com/articles/light-year) from the Sun – a comparatively wide uncertainty for a relatively nearby star.\nIts [absolute magnitude](https://bliptext.com/articles/absolute-magnitude) is about −6.\nWith an age of less than 10 million years, Betelgeuse has evolved rapidly because of its large mass, and is expected to end its evolution with a [supernova](https://bliptext.com/articles/supernova) explosion, most likely within 100,000 years.\nWhen Betelgeuse explodes, it will shine as bright as the [half-Moon](https://bliptext.com/articles/lunar-phase) for more than three months; life on Earth will be unharmed.\nHaving been ejected from its birthplace in the [Orion OB1 association](https://bliptext.com/articles/orion-ob1-association) – which includes the stars in [Orion's Belt](https://bliptext.com/articles/orion-s-belt) – this [runaway star](https://bliptext.com/articles/runaway-star) has been observed to be moving through the [interstellar medium](https://bliptext.com/articles/interstellar-medium) at a speed of 30 km/s, creating a [bow shock](https://bliptext.com/articles/bow-shocks-in-astrophysics) over four light-years wide.\nBetelgeuse became the first extrasolar star whose [photosphere](https://bliptext.com/articles/photosphere)'s angular size was measured in 1920, and subsequent studies have reported an [angular diameter](https://bliptext.com/articles/angular-diameter) (i.e., apparent size) ranging from 0.042 to 0.056 [arcseconds](https://bliptext.com/articles/minute-of-arc); that range of determinations is ascribed to non-sphericity, [limb darkening](https://bliptext.com/articles/limb-darkening), [pulsations](https://bliptext.com/articles/stellar-pulsations) and varying appearance at different [wavelengths](https://bliptext.com/articles/electromagnetic-radiation).\nIt is also surrounded by a complex, asymmetric [envelope](https://bliptext.com/articles/circumstellar-envelope), roughly 250 times the size of the star, caused by [mass loss](https://bliptext.com/articles/stellar-mass-loss) from the star itself.\nThe Earth-observed angular diameter of Betelgeuse is exceeded only by those of [R Doradus](https://bliptext.com/articles/r-doradus) and the Sun.\nStarting in October 2019, Betelgeuse began to dim noticeably, and by mid-February 2020 its brightness had dropped by a factor of approximately 3, from magnitude 0.5 to 1.7.\nIt then returned to a more normal brightness range, reaching a peak of 0.0 visual and 0.1 V-band magnitude in April 2023.\nInfrared observations found no significant change in [luminosity](https://bliptext.com/articles/bolometric-luminosity) over the last 50 years, suggesting that the dimming was due to a change in [extinction](https://bliptext.com/articles/extinction-astronomy) around the star rather than a more fundamental change.\nA study using the [Hubble Space Telescope](https://bliptext.com/articles/hubble-space-telescope) suggests that occluding dust was created by a surface mass ejection; this material was cast millions of miles from the star, and then cooled to form the dust that caused the dimming.\n\n# Nomenclature\nThe star's [designation](https://bliptext.com/articles/bayer-designation) is α Orionis (Latinised to Alpha Orionis), given by [Johann Bayer](https://bliptext.com/articles/johann-bayer) in 1603.\nThe traditional name Betelgeuse was derived from the [Arabic](https://bliptext.com/articles/arabic-language) يد الجوزاء \"the hand of al-Jawzā’ [i.e. Orion]\".\nAn error in the 13th-century reading of the Arabic initial [ي|yā’](https://bliptext.com/articles/y) (يـ) as [ب|bā’](https://bliptext.com/articles/b) (بـ—a difference in [i‘jām](https://bliptext.com/articles/arabic-diacritics)) led to the European name.\nIn English, there are four common pronunciations of this name, depending on whether the first e is pronounced short or long and whether the s is pronounced or :\nIn 2016, the [International Astronomical Union](https://bliptext.com/articles/international-astronomical-union) organized a [Working Group on Star Names](https://bliptext.com/articles/iau-working-group-on-star-names) (WGSN) to catalog and standardize proper names for stars.\nThe WGSN's first bulletin, issued July 2016, included a table of the first two batches of names approved by the WGSN, which included Betelgeuse for this star.\nIt is now so entered in the [IAU Catalog of Star Names](https://bliptext.com/articles/iau-working-group-on-star-names).\n\n# Observational history\nBetelgeuse and its red coloration have been noted since [antiquity](https://bliptext.com/articles/classical-antiquity); the classical astronomer [Ptolemy](https://bliptext.com/articles/ptolemy) described its color as ὑπόκιρρος (hypókirrhos = more or less orange-tawny), a term later described by a translator of [Ulugh Beg](https://bliptext.com/articles/ulugh-beg)'s [Zij-i Sultani](https://bliptext.com/articles/zij-i-sultani) as rubedo, [Latin](https://bliptext.com/articles/latin) for \"ruddiness\".\nIn the 19th century, before modern systems of [stellar classification](https://bliptext.com/articles/stellar-classification), [Angelo Secchi](https://bliptext.com/articles/angelo-secchi) included Betelgeuse as one of the prototypes for his [Class III](https://bliptext.com/articles/secchi-classes) (orange to red) stars.\nThree centuries before Ptolemy, in contrast, Chinese astronomers observed Betelgeuse as yellow; Such an observation, if accurate, could suggest the star was in a [yellow supergiant](https://bliptext.com/articles/yellow-supergiant) phase around this time, a credible possibility, given current research into these stars' complex circumstellar environment.\n\n## Nascent discoveries\nAboriginal groups in South Australia have shared oral tales of the variable brightness of Betelgeuse for at least 1,000 years.\nThe variation in Betelgeuse's brightness was described in 1836 by [Sir John Herschel](https://bliptext.com/articles/john-herschel) in Outlines of Astronomy.\nFrom 1836 to 1840, he noticed significant changes in magnitude when Betelgeuse outshone [Rigel](https://bliptext.com/articles/rigel) in October 1837 and again in November 1839.\nA 10-year quiescent period followed; then in 1849, Herschel noted another short cycle of variability, which peaked in 1852.\nLater observers recorded unusually high [maxima](https://bliptext.com/articles/maxima-and-minima) with an interval of years, but only small variations from 1957 to 1967.\nThe records of the [American Association of Variable Star Observers](https://bliptext.com/articles/american-association-of-variable-star-observers) (AAVSO) show a maximum [brightness](https://bliptext.com/articles/apparent-magnitude) of 0.2 in 1933 and 1942, and a minimum of 1.2, observed in 1927 and 1941.\nThis variability in brightness may explain why [Johann Bayer](https://bliptext.com/articles/johann-bayer), with the publication of his [Uranometria](https://bliptext.com/articles/uranometria) in 1603, designated the star alpha, as it probably rivaled the usually brighter Rigel (beta).\nFrom Arctic latitudes, Betelgeuse's red colour and higher location in the sky than Rigel meant the [Inuit](https://bliptext.com/articles/inuit) regarded it as brighter, and one local name was Ulluriajjuaq (\"large star\").\nIn 1920, [Albert A. Michelson](https://bliptext.com/articles/albert-a-michelson) and [Francis G. Pease](https://bliptext.com/articles/francis-g-pease) mounted a six-meter [interferometer](https://bliptext.com/articles/interferometry) on the front of the 2.5-meter telescope at [Mount Wilson Observatory](https://bliptext.com/articles/mount-wilson-observatory), helped by [John August Anderson](https://bliptext.com/articles/john-august-anderson).\nThe trio measured the angular diameter of Betelgeuse at 0.047[″](https://bliptext.com/articles/arcsecond), a figure that resulted in a diameter of 3.84 km (2.58 AU) based on the [parallax](https://bliptext.com/articles/stellar-parallax) value of 0.018 \". But limb darkening and measurement errors resulted in uncertainty about the accuracy of these measurements.\nThe 1950s and 1960s saw two developments that affected stellar [convection](https://bliptext.com/articles/convection) theory in red supergiants: the [Stratoscope](https://bliptext.com/articles/stratoscope) projects and the 1958 publication of Structure and Evolution of the Stars, principally the work of [Martin Schwarzschild](https://bliptext.com/articles/martin-schwarzschild) and his colleague at [Princeton University](https://bliptext.com/articles/princeton-university), Richard Härm.\nThis book disseminated ideas on how to apply computer technologies to create stellar models, while the Stratoscope projects, by taking balloon-borne telescopes above the Earth's [turbulence](https://bliptext.com/articles/wave-turbulence), produced some of the finest images of [solar granules](https://bliptext.com/articles/solar-granule) and [sunspots](https://bliptext.com/articles/sunspot) ever seen, thus confirming the existence of convection in the solar atmosphere.\n# [Sir John Herschel in 1846 | upload.wikimedia.org/wikipedia/commons/6/62/John///Herschel///1846///%28cropped%29.png]\n\n## Imaging breakthroughs\nAstronomers saw some major advances in astronomical imaging technology in the 1970s, beginning with [Antoine Labeyrie](https://bliptext.com/articles/antoine-mile-henry-labeyrie)'s invention of [speckle interferometry](https://bliptext.com/articles/speckle-interferometry), a process that significantly reduced the blurring effect caused by [astronomical seeing](https://bliptext.com/articles/astronomical-seeing).\nIt increased the [optical resolution](https://bliptext.com/articles/optical-resolution) of ground-based [telescopes](https://bliptext.com/articles/telescope), allowing for more precise measurements of Betelgeuse's photosphere.\nWith improvements in [infrared telescopy](https://bliptext.com/articles/infrared-telescopy) atop [Mount Wilson](https://bliptext.com/articles/mount-wilson-observatory), [Mount Locke](https://bliptext.com/articles/mcdonald-observatory), and [Mauna Kea](https://bliptext.com/articles/mauna-kea-observatories) in Hawaii, astrophysicists began peering into the complex circumstellar shells surrounding the supergiant, causing them to suspect the presence of huge gas bubbles resulting from convection.\nHowever, it was not until the late 1980s and early 1990s, when Betelgeuse became a regular target for [aperture masking interferometry](https://bliptext.com/articles/aperture-masking-interferometry), that breakthroughs occurred in visible-light and [infrared imaging](https://bliptext.com/articles/infrared-photography).\nPioneered by [J.E. Baldwin](https://bliptext.com/articles/john-e-baldwin) and colleagues of the [Cavendish Astrophysics Group](https://bliptext.com/articles/cavendish-astrophysics-group), the new technique employed a small mask with several holes in the telescope pupil plane, converting the [aperture](https://bliptext.com/articles/aperture) into an ad hoc interferometric array.\nThe technique contributed some of the most accurate measurements of Betelgeuse while revealing bright spots on the star's photosphere.\nThese were the first optical and infrared images of a stellar disk other than the [Sun](https://bliptext.com/articles/sun), taken first from ground-based interferometers and later from higher-resolution observations of the [COAST telescope](https://bliptext.com/articles/cambridge-optical-aperture-synthesis-telescope).\nThe \"bright patches\" or \"hotspots\" observed with these instruments appeared to corroborate a theory put forth by Schwarzschild decades earlier of massive [convection](https://bliptext.com/articles/convection-zone) cells dominating the stellar surface.\nIn 1995, the [Hubble Space Telescope](https://bliptext.com/articles/hubble-space-telescope)'s [Faint Object Camera](https://bliptext.com/articles/faint-object-camera) captured an [ultraviolet image](https://bliptext.com/articles/ultraviolet-astronomy) with a resolution superior to that obtained by ground-based interferometers—the first conventional-telescope image (or \"direct-image\" in NASA terminology) of the disk of another star.\nBecause [ultraviolet](https://bliptext.com/articles/ultraviolet) light is absorbed by the [Earth's atmosphere](https://bliptext.com/articles/atmosphere-of-earth), observations at these wavelengths are best performed by [space telescopes](https://bliptext.com/articles/space-telescope).\nThis image, like earlier pictures, contained a bright patch indicating a region in the southwestern quadrant 2,000 K hotter than the stellar surface.\nSubsequent ultraviolet spectra taken with the [Goddard High Resolution Spectrograph](https://bliptext.com/articles/goddard-high-resolution-spectrograph) suggested that the hot spot was one of Betelgeuse's poles of rotation.\nThis would give the rotational axis an inclination of about 20° to the direction of Earth, and a [position angle](https://bliptext.com/articles/position-angle) from [celestial North](https://bliptext.com/articles/celestial-pole) of about 55°.\n# [1998/9 UV HST images of Betelgeuse showing asymmetrical pulsations with corresponding spectral line profiles | upload.wikimedia.org/wikipedia/commons/4/43/Betelgeuse///pulsating///UV///%28HST%29.jpg]\n\n## 2000s studies\nIn a study published in December 2000, the star's diameter was measured with the [Infrared Spatial Interferometer](https://bliptext.com/articles/infrared-spatial-interferometer) (ISI) at mid-infrared wavelengths producing a limb-darkened estimate of 55.2 mas – a figure entirely consistent with Michelson's findings eighty years earlier.\nAt the time of its publication, the estimated parallax from the [Hipparcos](https://bliptext.com/articles/hipparcos) mission was 7.63 mas, yielding an estimated radius for Betelgeuse of 3.6 AU.\nHowever, an infrared interferometric study published in 2009 announced that the star had shrunk by 15% since 1993 at an increasing rate without a significant diminution in magnitude.\nSubsequent observations suggest that the apparent contraction may be due to shell activity in the star's extended atmosphere.\nIn addition to the star's diameter, questions have arisen about the complex dynamics of Betelgeuse's extended atmosphere.\nThe mass that makes up galaxies is recycled as [stars are formed and destroyed](https://bliptext.com/articles/life-cycle-of-stars), and red supergiants are major contributors, yet the process by which mass is lost remains a mystery.\nWith advances in interferometric methodologies, astronomers may be close to resolving this conundrum.\nImages released by the [European Southern Observatory](https://bliptext.com/articles/european-southern-observatory) in July 2009, taken by the ground-based [Very Large Telescope](https://bliptext.com/articles/very-large-telescope) Interferometer (VLTI), showed a vast plume of gas extending 30 AU from the star into the surrounding atmosphere.\nThis mass ejection was equal to the distance between the Sun and [Neptune](https://bliptext.com/articles/neptune) and is one of multiple events occurring in Betelgeuse's surrounding atmosphere.\nAstronomers have identified at least six shells surrounding Betelgeuse.\nSolving the mystery of mass loss in the late stages of a star's evolution may reveal those factors that precipitate the explosive deaths of these stellar giants.\n\n## 2019–2020 fading\nA pulsating [semiregular variable star](https://bliptext.com/articles/semiregular-variable-star), Betelgeuse is subject to multiple cycles of increasing and decreasing brightness due to changes in its size and temperature.\nThe astronomers who first noted the dimming of Betelgeuse, [Villanova University](https://bliptext.com/articles/villanova-university) astronomers Richard Wasatonic and [Edward Guinan](https://bliptext.com/articles/edward-guinan), and amateur Thomas Calderwood, theorize that a coincidence of a normal 5.9 year light-cycle minimum and a deeper-than-normal 425 day period are the driving factors.\nOther possible causes hypothesized by late 2019 were an eruption of gas or dust or fluctuations in the star's surface brightness.\nBy August 2020, long-term and extensive studies of Betelgeuse, primarily using [ultraviolet observations](https://bliptext.com/articles/ultraviolet-astronomy) by the [Hubble Space Telescope](https://bliptext.com/articles/hubble-space-telescope), had suggested that the unexpected dimming was probably caused by an immense amount of superhot material ejected into space.\nThe material cooled and formed a dust cloud that blocked the starlight coming from about a quarter of Betelgeuse's surface.\nHubble captured signs of dense, heated material moving through the star's atmosphere in September, October and November before several telescopes observed the more marked dimming in December and the first few months of 2020.\nBy January 2020, Betelgeuse had dimmed by a factor of approximately 2.5 from magnitude 0.5 to 1.5 and was reported still fainter in February in [The Astronomer's Telegram](https://bliptext.com/articles/the-astronomer-s-telegram) at a record minimum of +1.614, noting that the star is currently the \"least luminous and coolest\" in the 25 years of their studies and also calculating a decrease in radius.\n[Astronomy](https://bliptext.com/articles/astronomy-magazine) magazine described it as a \"bizarre dimming\",\nand popular speculation inferred that this might indicate an imminent [supernova](https://bliptext.com/articles/supernova).\nThis dropped Betelgeuse from one of the top 10 [brightest stars in the sky](https://bliptext.com/articles/list-of-brightest-stars) to outside the top 20, noticeably dimmer than its near neighbor [Aldebaran](https://bliptext.com/articles/aldebaran).\nMainstream media reports discussed speculation that Betelgeuse might be about to explode as a supernova,\nbut astronomers note that the supernova is expected to occur within approximately the next 100,000 years and is thus unlikely to be imminent.\nBy 17 February 2020, Betelgeuse's brightness had remained constant for about 10 days, and the star showed signs of rebrightening.\nOn 22 February 2020, Betelgeuse may have stopped dimming altogether, all but ending the dimming episode.\nOn 24 February 2020, no significant change in the infrared over the last 50 years was detected; this seemed unrelated to the recent visual fading and suggested that an impending core collapse may be unlikely.\nAlso on 24 February 2020, further studies suggested that occluding \"large-grain [circumstellar dust](https://bliptext.com/articles/circumstellar-dust)\" may be the most likely explanation for the dimming of the star.\nA study that uses [observations](https://bliptext.com/articles/observation) at [submillimetre](https://bliptext.com/articles/submillimetre-astronomy) wavelengths rules out significant contributions from dust absorption.\nInstead, large [starspots](https://bliptext.com/articles/starspot) appear to be the cause for the dimming.\nFollowup studies, reported on 31 March 2020 in The Astronomer's Telegram, found a rapid rise in the brightness of Betelgeuse.\nBetelgeuse is almost unobservable from the ground between May and August because it is too close to the Sun.\nBefore entering its 2020 [conjunction](https://bliptext.com/articles/conjunction-astronomy) with the Sun, Betelgeuse had reached a brightness of +0.4.\nObservations with the [STEREO-A](https://bliptext.com/articles/stereo) spacecraft made in June and July 2020 showed that the star had dimmed by 0.5 since the last ground-based observation in April.\nThis is surprising, because a maximum was expected for August/September 2020, and the next minimum should occur around April 2021.\nHowever Betelgeuse's brightness is known to vary irregularly, making predictions difficult.\nThe fading could indicate that another dimming event might occur much earlier than expected.\nOn 30 August 2020, astronomers reported the detection of a second dust cloud emitted from Betelgeuse, and associated with recent substantial dimming (a secondary minimum on 3 August) in luminosity of the star.\nIn June 2021, the dust was explained as possibly caused by a cool patch on its photosphere\nand in August a second independent group confirmed these results.\nThe dust is thought to have resulted from the cooling of gas ejected from the star.\nAn August 2022\nstudy using the [Hubble Space Telescope](https://bliptext.com/articles/hubble-space-telescope) confirmed previous research and suggested the dust could have been created by a surface mass ejection.\nIt conjectured as well that the dimming could have come from a short-term minimum coinciding with a long-term minimum producing a grand minimum, a 416-day cycle and 2010 day cycle respectively, a mechanism first suggested by astronomer [L. Goldberg](https://bliptext.com/articles/leo-goldberg).\nIn April 2023, astronomers reported the star reached a peak of 0.0 visual and 0.1 V-band magnitude.\n# [AAVSO V-band magnitude of Betelgeuse, between September 2016 and August 2023 | upload.wikimedia.org/wikipedia/commons/5/50/Betelgeuse///AAVSO///2019.jpg]\n# [Comparison of SPHERE images of Betelgeuse taken in January 2019 and December 2019, showing the changes in brightness and shape | upload.wikimedia.org/wikipedia/commons/0/0e/Eso2003c.jpg]\n\n# Observation\nAs a result of its distinctive orange-red color and position within Orion, Betelgeuse is easy to find with the naked eye.\nIt is one of three stars that make up the [Winter Triangle](https://bliptext.com/articles/winter-triangle) [asterism](https://bliptext.com/articles/asterism-astronomy), and it marks the center of the [Winter Hexagon](https://bliptext.com/articles/winter-hexagon).\nIt can be seen rising in the east at the beginning of January of each year, just after sunset.\nBetween mid-September and mid-March (best in mid-December), it is visible to virtually every inhabited region of the globe, except in [Antarctica](https://bliptext.com/articles/antarctica) at latitudes south of 82°.\nIn May (moderate northern latitudes) or June (southern latitudes), the red supergiant can be seen briefly on the western horizon after sunset, reappearing again a few months later on the eastern horizon before sunrise.\nIn the intermediate period (June–July, centered around mid June), it is invisible to the naked eye (visible only with a telescope in daylight), except around midday low in the north in Antarctic regions between 70° and 80° south latitude (during midday twilight in [polar night](https://bliptext.com/articles/polar-night), when the Sun is below the horizon).\nBetelgeuse is a variable star whose [visual magnitude](https://bliptext.com/articles/apparent-magnitude) ranges between 0.0 and +1.6.\nThere are periods during which it surpasses Rigel to become the sixth brightest star, and occasionally it will become even brighter than [Capella](https://bliptext.com/articles/capella).\nAt its faintest, Betelgeuse can fall behind [Deneb](https://bliptext.com/articles/deneb) and [Beta Crucis](https://bliptext.com/articles/beta-crucis), themselves both slightly variable, to be the twentieth-brightest star.\nBetelgeuse has a B–V [color index](https://bliptext.com/articles/color-index) of 1.85 – a figure which points to its pronounced \"redness\".\nThe photosphere has an extended [atmosphere](https://bliptext.com/articles/stellar-atmosphere), which displays strong lines of [emission](https://bliptext.com/articles/spectral-line) rather than [absorption](https://bliptext.com/articles/spectral-line), a phenomenon that occurs when a star is surrounded by a thick gaseous envelope (rather than ionized).\nThis extended gaseous atmosphere has been observed moving toward and away from Betelgeuse, depending on fluctuations in the photosphere.\nBetelgeuse is the brightest near-infrared source in the sky with a [J band](https://bliptext.com/articles/j-band-infrared) [magnitude](https://bliptext.com/articles/magnitude-astronomy) of −2.99; only about 13% of the star's [radiant energy](https://bliptext.com/articles/radiant-energy) is emitted as visible light.\nIf human eyes were sensitive to radiation at all wavelengths, Betelgeuse would appear as the brightest star in the night sky.\nCatalogues list up to nine faint visual companions to Betelgeuse.\nThey are at distances of about one to four arc-minutes and all are fainter than 10th magnitude.\n# [Image showing Betelgeuse (top left) and the dense nebulae of the Orion molecular cloud complex ( Rogelio Bernal Andreo ) | upload.wikimedia.org/wikipedia/commons/4/47/Orion///Head///to///Toe.jpg]\n# [Orion as seen on midday mid-June from Dome C (75 degrees South, Antarctica). Screenshot from Stellarium | upload.wikimedia.org/wikipedia/commons/0/08/Orion///from///Antarctica///in///polar///night.png]\n\n## Star system\nBetelgeuse is generally considered to be a single isolated star and a [runaway star](https://bliptext.com/articles/runaway-star), not currently associated with any cluster or star-forming region, although its birthplace is unclear.\nTwo spectroscopic companions to Betelgeuse have been proposed.\nAnalysis of [polarization](https://bliptext.com/articles/polarization-waves) data from 1968 through 1983 indicated a close companion with a periodic orbit of about 2.1 years, and by using [speckle interferometry](https://bliptext.com/articles/speckle-imaging), the team concluded that the closer of the two companions was located at 0.06 \" (≈9 AU) from the main star with a position angle of 273°, an orbit that would potentially place it within the star's [chromosphere](https://bliptext.com/articles/chromosphere). The more distant companion was at 0.51 \" (≈77 AU) with a position angle of 278°.\nFurther studies have found no evidence for these companions or have actively refuted their existence, but the possibility of a close companion contributing to the overall flux has never been fully ruled out.\nHigh-resolution interferometry of Betelgeuse and its vicinity, far beyond the technology of the 1980s and 1990s, has not detected any companions.\nA more recent study found that a not yet directly-observed, dust-modulating stellar-mass companion of would be the most likely solution for Betelgeuse's 2170-day secondary periodicity, fluctuating radial velocity, moderate radius and low variation in effective temperature.\nThe candidate companion would have a semi-major axis of 8.6 [AU](https://bliptext.com/articles/astronomical-unit).\n\n## Distance measurements\n[Parallax](https://bliptext.com/articles/parallax) is the apparent change of the position of an object, measured in seconds of arc, caused by the change of position of the observer of that object.\nAs the Earth orbits the Sun, every star is seen to shift by a fraction of an arc second, which measure, combined with the baseline provided by the Earth's orbit gives the distance to that star.\nSince the first successful [parallax](https://bliptext.com/articles/parallax) measurement by [Friedrich Bessel](https://bliptext.com/articles/friedrich-bessel) in 1838, astronomers have been puzzled by Betelgeuse's apparent distance.\nKnowledge of the star's distance improves the accuracy of other stellar parameters, such as [luminosity](https://bliptext.com/articles/stellar-luminosity) that, when combined with an angular diameter, can be used to calculate the physical radius and [effective temperature](https://bliptext.com/articles/effective-temperature); [luminosity](https://bliptext.com/articles/stellar-luminosity) and [isotopic abundances](https://bliptext.com/articles/natural-abundance) can also be used to estimate the [stellar age](https://bliptext.com/articles/stellar-evolution) and [mass](https://bliptext.com/articles/intermediate-mass-star).\nWhen the first interferometric studies were performed on the star's diameter in 1920, the assumed parallax was 0.018 \". This equated to a distance of 56 pc or roughly 180 ly, producing not only an inaccurate radius for the star but every other stellar characteristic. Since then, there has been ongoing work to measure the distance of Betelgeuse, with proposed distances as high as 400 pc or about 1,300 ly.\nBefore the publication of the [Hipparcos Catalogue](https://bliptext.com/articles/hipparcos-catalogue) (1997), there were two slightly conflicting parallax measurements for Betelgeuse.\nThe first, in 1991, gave a parallax of 9.8 mas, yielding a distance of roughly 102 pc or 330 ly.\nThe second was the [Hipparcos Input Catalogue](https://bliptext.com/articles/hipparcos) (1993) with a trigonometric parallax of 5 mas, a distance of 200 pc or 650 ly.\nGiven this uncertainty, researchers were adopting a wide range of distance estimates, leading to significant variances in the calculation of the star's attributes.\nThe results from the Hipparcos mission were released in 1997.\nThe measured parallax of Betelgeuse was 7.63 mas, which equated to a distance of roughly 131 pc or 427 ly, and had a smaller reported error than previous measurements.\nHowever, later evaluation of the Hipparcos parallax measurements for variable stars like Betelgeuse found that the uncertainty of these measurements had been underestimated.\nIn 2007, an improved figure of 6.55 was calculated, hence a much tighter [error factor](https://bliptext.com/articles/margin-of-error) yielding a distance of roughly 152 pc or 500 ly.\nIn 2008, measurements using the [Very Large Array](https://bliptext.com/articles/very-large-array) (VLA) produced a [radio](https://bliptext.com/articles/radio-astronomy) solution of 5.07 mas, equaling a distance of 197 pc or 643 ly.\nAs the researcher, Harper, points out: \"The revised Hipparcos parallax leads to a larger distance (152 pc) than the original; however, the [astrometric](https://bliptext.com/articles/astrometric) solution still requires a significant [cosmic noise](https://bliptext.com/articles/cosmic-noise) of 2.4 mas. Given these results it is clear that the Hipparcos data still contain systematic errors of unknown origin.\"\nAlthough the radio data also have systematic errors, the Harper solution combines the datasets in the hope of mitigating such errors.\nAn updated result from further observations with [ALMA](https://bliptext.com/articles/atacama-large-millimeter-array) and [e-Merlin](https://bliptext.com/articles/e-merlin) gives a parallax of 4.51 mas and a distance of 222 pc or 724 ly.\nIn 2020, new observational data from the space-based Solar Mass Ejection Imager aboard the [Coriolis satellite](https://bliptext.com/articles/coriolis-satellite) and three different modeling techniques produced a refined parallax of 5.95 mas, a radius of 764, and a distance of 168.1 pc or 548 ly, which, if accurate, would mean Betelgeuse is nearly 25% smaller and 25% closer to Earth than previously thought.\nAlthough the [European Space Agency](https://bliptext.com/articles/european-space-agency)'s current [Gaia mission](https://bliptext.com/articles/gaia-mission) was not expected to produce good results for stars brighter than the approximately V=6 saturation limit of the mission's instruments, actual operation has shown good performance on objects to about magnitude +3.\nForced observations of brighter stars mean that final results should be available for all bright stars and a parallax for Betelgeuse will be published an order of magnitude more accurate than currently available.\nThere is no data on Betelgeuse in [Gaia Data Release 2](https://bliptext.com/articles/gaia-data-release-2), which was released in 2018.\n# [NRAO's Very Large Array used to derive Betelgeuse's 2008 distance estimate | upload.wikimedia.org/wikipedia/commons/6/63/USA.NM.VeryLargeArray.02.jpg]\n\n## Variability\nBetelgeuse is classified as a [semiregular variable star](https://bliptext.com/articles/semiregular-variable-star), indicating that some periodicity is noticeable in the brightness changes, but amplitudes may vary, cycles may have different lengths, and there may be standstills or periods of irregularity.\nIt is placed in subgroup SRc; these are pulsating red supergiants with amplitudes around one magnitude and periods from tens to hundreds of days.\nBetelgeuse typically shows only small brightness changes near to magnitude +0.5, although at its extremes it can become as bright as magnitude 0.0 or as faint as magnitude +1.6.\nBetelgeuse is listed in the [General Catalogue of Variable Stars](https://bliptext.com/articles/general-catalogue-of-variable-stars) with a possible period of 2,335 days.\nMore detailed analyses have shown a main period near 400 days, a short period of 185 days, and a longer secondary period around 2,100 days.\nThe lowest reliably-recorded [V-band](https://bliptext.com/articles/ubv-photometric-system) magnitude of +1.614 was reported in February 2020.\nRadial pulsations of red supergiants are well-modelled and show that periods of a few hundred days are typically due to [fundamental](https://bliptext.com/articles/fundamental-mode) and first [overtone](https://bliptext.com/articles/overtone) pulsation.\n[Lines](https://bliptext.com/articles/absorption-line) in the [spectrum](https://bliptext.com/articles/stellar-spectrum) of Betelgeuse show [doppler shifts](https://bliptext.com/articles/doppler-shift) indicating [radial velocity](https://bliptext.com/articles/radial-velocity) changes corresponding, very roughly, to the brightness changes.\nThis demonstrates the nature of the pulsations in size, although corresponding temperature and spectral variations are not clearly seen.\nVariations in the diameter of Betelgeuse have also been measured directly.\n[First overtone](https://bliptext.com/articles/overtone) pulsations of 185 days have been observed, and the ratio of the fundamental to overtone periods gives valuable information about the internal structure of the star and its age.\nThe source of the long secondary periods is unknown, but they cannot be explained by [radial pulsations](https://bliptext.com/articles/radial-pulsations).\nInterferometric observations of Betelgeuse have shown hotspots that are thought to be created by massive convection cells, a significant fraction of the diameter of the star and each emitting 5–10% of the total light of the star.\nOne theory to explain long secondary periods is that they are caused by the evolution of such cells combined with the rotation of the star.\nOther theories include close binary interactions, [chromospheric](https://bliptext.com/articles/chromosphere) magnetic activity influencing mass loss, or non-radial pulsations such as [g-modes](https://bliptext.com/articles/g-mode-pulsation).\nIn addition to the discrete dominant periods, small-amplitude [stochastic](https://bliptext.com/articles/stochastic) variations are seen.\nIt is proposed that this is due to [granulation](https://bliptext.com/articles/granule-solar-physics), similar to the same effect on the sun but on a much larger scale.\n# [AAVSO V-band light curve of Betelgeuse (Alpha Orionis) from Dec 1988 to Aug 2002 | upload.wikimedia.org/wikipedia/commons/b/b7/Light///curve///of///Betelgeuse.png]\n# [Orion, with Betelgeuse at its usual magnitude (left) and during the unusually deep minimum in early 2020 (right) | upload.wikimedia.org/wikipedia/commons/a/ac/Betelgeuse.jpg]\n\n## Diameter\nOn 13 December 1920, Betelgeuse became the first star outside the Solar System to have the angular size of its photosphere measured.\nAlthough interferometry was still in its infancy, the experiment proved a success.\nThe researchers, using a uniform disk model, determined that Betelgeuse had a diameter of 0.047 \", although the stellar disk was likely 17% larger due to the [limb darkening](https://bliptext.com/articles/limb-darkening), resulting in an estimate for its angular diameter of about 0.055\".\nSince then, other studies have produced angular diameters that range from 0.042 to 0.069 \". Combining these data with historical distance estimates of 180 to 815 ly yields a projected radius of the stellar disk of anywhere from 1.2 to 8.9 AU. Using the Solar System for comparison, the orbit of [Mars](https://bliptext.com/articles/solar-system) is about 1.5 AU, [Ceres](https://bliptext.com/articles/solar-system) in the [asteroid belt](https://bliptext.com/articles/asteroid-belt) 2.7 AU, [Jupiter](https://bliptext.com/articles/solar-system) 5.5 AU—so, assuming Betelgeuse occupying the place of the Sun, its photosphere might extend beyond the Jovian orbit, not quite reaching [Saturn](https://bliptext.com/articles/solar-system) at 9.5 AU.\nThe precise diameter has been hard to define for several reasons:\nThe generally reported radii of large cool stars are [Rosseland radii](https://bliptext.com/articles/rosseland-optical-depth), defined as the radius of the photosphere at a specific optical depth of two-thirds.\nThis corresponds to the radius calculated from the effective temperature and bolometric luminosity.\nThe Rosseland radius differs from directly measured radii, with corrections for [limb darkening](https://bliptext.com/articles/limb-darkening) and the observation wavelength.\nFor example, a measured angular diameter of 55.6 mas would correspond to a Rosseland mean diameter of 56.2 mas, while further corrections for the existence of surrounding dust and gas shells would give a diameter of 41.9 mas.\nTo overcome these challenges, researchers have employed various solutions.\nAstronomical interferometry, first conceived by [Hippolyte Fizeau](https://bliptext.com/articles/hippolyte-fizeau) in 1868, was the seminal concept that has enabled major improvements in modern telescopy and led to the creation of the [Michelson interferometer](https://bliptext.com/articles/michelson-interferometer) in the 1880s, and the first successful measurement of Betelgeuse.\nJust as human [depth perception](https://bliptext.com/articles/depth-perception) increases when two eyes instead of one perceive an object, Fizeau proposed the observation of stars through two [apertures](https://bliptext.com/articles/apertures) instead of one to obtain [interferences](https://bliptext.com/articles/interference-wave-propagation) that would furnish information on the star's spatial intensity distribution.\nThe science evolved quickly and multiple-aperture interferometers are now used to capture [speckled images](https://bliptext.com/articles/speckle-imaging), which are synthesized using [Fourier analysis](https://bliptext.com/articles/fourier-analysis) to produce a portrait of high resolution.\nIt was this methodology that identified the hotspots on Betelgeuse in the 1990s.\nOther technological breakthroughs include [adaptive optics](https://bliptext.com/articles/adaptive-optics), [space observatories](https://bliptext.com/articles/space-observatory) like Hipparcos, [Hubble](https://bliptext.com/articles/hubble-space-telescope) and [Spitzer](https://bliptext.com/articles/spitzer-space-telescope), and the [Astronomical Multi-BEam Recombiner (AMBER)](https://bliptext.com/articles/amber-very-large-telescope), which combines the beams of three telescopes simultaneously, allowing researchers to achieve milliarcsecond [spatial resolution](https://bliptext.com/articles/spatial-resolution).\nObservations in different regions of the electromagnetic spectrum—the visible, near-infrared ([NIR](https://bliptext.com/articles/infrared)), mid-infrared (MIR), or radio—produce very different angular measurements.\nIn 1996, Betelgeuse was shown to have a uniform disk of 56.6 mas.\nIn 2000, a [Space Sciences Laboratory](https://bliptext.com/articles/space-sciences-laboratory) team measured a diameter of 54.7 mas, ignoring any possible contribution from hotspots, which are less noticeable in the mid-infrared.\nAlso included was a theoretical allowance for limb darkening, yielding a diameter of 55.2 mas.\nThe earlier estimate equates to a radius of roughly 5.6 AU or, assuming the 2008 Harper distance of 197 pc, a figure roughly the size of the Jovian orbit of 5.5 AU.\nIn 2004, a team of astronomers working in the near-infrared announced that the more accurate photospheric measurement was 43.33 mas.\nThe study also put forth an explanation as to why varying wavelengths from the visible to mid-infrared produce different diameters: the star is seen through a thick, warm extended atmosphere.\nAt short wavelengths (the visible spectrum) the atmosphere scatters light, thus slightly increasing the star's diameter.\nAt near-infrared wavelengths ([K](https://bliptext.com/articles/k-band-infrared) and [L bands](https://bliptext.com/articles/l-band-infrared)), the scattering is negligible, so the classical photosphere can be directly seen; in the mid-infrared the scattering increases once more, causing the thermal emission of the warm atmosphere to increase the apparent diameter.\nStudies with the [IOTA](https://bliptext.com/articles/infrared-optical-telescope-array) and VLTI published in 2009 brought strong support to the idea of dust shells and a molecular shell (MOLsphere) around Betelgeuse, and yielded diameters ranging from 42.57 to 44.28 mas with comparatively insignificant margins of error.\nIn 2011, a third estimate in the near-infrared corroborating the 2009 numbers, this time showing a limb-darkened disk diameter of 42.49 mas.\nThe near-infrared photospheric diameter of 43.33 mas at the Hipparcos distance of 152 pc equates to about 3.4 AU or.\nA 2014 paper derives an angular diameter of 42.28 mas (equivalent to a 41.01 mas uniform disc) using H and K band observations made with the VLTI AMBER instrument.\nIn 2009 it was announced that the radius of Betelgeuse had shrunk from 1993 to 2009 by 15%, with the 2008 angular measurement equal to 47 mas.\nUnlike most earlier papers, this study used measurements at one specific wavelength over 15 years.\nThe diminution in Betelgeuse's [apparent size](https://bliptext.com/articles/apparent-size) equates to a range of values between 56 mas seen in 1993 to 47 mas seen in 2008—a contraction of almost 0.9 AU in 15 years.\nThe observed contraction is generally believed to be a variation in just a portion of the extended atmosphere around Betelgeuse, and observations at other wavelengths have shown an increase in diameter over a similar period.\nThe latest models of Betelgeuse adopt a photospheric angular diameter of around 43 mas, with multiple shells out to 50–60 mas.\nAssuming a distance of 197 pc, this means a stellar diameter of 887 R_solar.\nOnce considered as having the largest angular diameter of any star in the sky after the [Sun](https://bliptext.com/articles/sun), Betelgeuse lost that distinction in 1997 when a group of astronomers measured [R Doradus](https://bliptext.com/articles/r-doradus) with a diameter of 57 mas, although [R Doradus](https://bliptext.com/articles/r-doradus), being much closer to Earth at about 200 ly, has a linear diameter roughly one-third that of Betelgeuse.\n# [Size comparison between Arcturus, Rigel, S Doradus, Antares, and Betelgeuse | upload.wikimedia.org/wikipedia/commons/0/03/Arcturus///to///Betelgeuse///comparison.jpg]\n# [Size comparison of Betelgeuse, Mu Cephei, KY Cygni, and V354 Cephei, according to Emily Levesque | upload.wikimedia.org/wikipedia/commons/5/50/Mukyv354.png]\n# [Radio image from 1998 showing the size of Betelgeuse's photosphere (circle) and the effect of convective forces on the star's atmosphere | upload.wikimedia.org/wikipedia/commons/7/75/Betelgeuse///radio///wavelengths.jpg]\n# [Infrared image of Betelgeuse, Meissa and Bellatrix with surrounding nebulae | upload.wikimedia.org/wikipedia/commons/d/d4/Orion%27s///Big///Head///Revealed///in///Infrared.jpg]\n\n## Occultations\nBetelgeuse is too far from the ecliptic to be occulted by the major planets, but those by some [asteroids](https://bliptext.com/articles/asteroid) (which are more wide-ranging and much more numerous) occur frequently.\nA partial occultation by the 19th magnitude asteroid occurred on 2 January 2012.\nIt was partial because the angular diameter of the star was larger than that of the asteroid; the brightness of Betelgeuse dropped by only about 0.01 magnitudes.\nThe 14th magnitude asteroid [319 Leona](https://bliptext.com/articles/319-leona) was predicted to occult on 12 December 2023, 01:12 UTC.\nTotality was at first uncertain, and the occulation was projected to only last approximately twelve seconds (visible on a narrow path on Earth's surface, the exact width and location of which was initially uncertain due to lack of precise knowledge of the size and path of the asteroid).\nProjections were later refined as more data were analyzed for a totality (\"ring of fire\") of approximately five seconds and a 60 km wide path stretching from Tajikistan, Armenia, Turkey, Greece, Italy, Spain, the Atlantic Ocean, Miami, Florida and the [Florida Keys](https://bliptext.com/articles/florida-keys) to parts of Mexico.\n(The serendiptous event would also afford detailed observations of 319 Leona itself.) Among other programmes 80 [amateur astronomers](https://bliptext.com/articles/citizen-science) in Europe alone have been coordinated by astrophysicist [Miguel Montargès](https://bliptext.com/articles/miguel-montarg-s), et al. of the [Paris Observatory](https://bliptext.com/articles/paris-observatory) for the event.\n# [Predicted path using SOLEX | upload.wikimedia.org/wikipedia/commons/6/6a/Leona///Betelgeuse.png]\n\n# Physical characteristics\nStar-sizes.jpg and several stars, including Betelgeuse: 1. Mercury < Mars < Venus < Earth\n2. Earth < Neptune < Uranus < Saturn < Jupiter\n3. Jupiter < Wolf 359 < Sun < Sirius\n4. Sirius < Pollux < Arcturus < Aldebaran\n5. Aldebaran < Rigel < Antares < Betelgeuse\n6. Betelgeuse < Mu Cephei < VV Cephei A < VY Canis Majoris\n]]\nBetelgeuse is a very large, luminous but cool star classified as an M1-2 Ia-ab [red supergiant](https://bliptext.com/articles/red-supergiant).\nThe letter \"M\" in this designation means that it is a red star belonging to the [M spectral class](https://bliptext.com/articles/class-m-star) and therefore has a relatively low photospheric temperature; the \"Ia-ab\" suffix [luminosity class](https://bliptext.com/articles/yerkes-spectral-classification-scheme) indicates that it is an intermediate-luminosity supergiant, with properties partway between a normal supergiant and a luminous supergiant.\nSince 1943, the spectrum of Betelgeuse has served as one of the stable anchor points by which other stars are classified.\nUncertainty in the star's surface temperature, diameter, and distance make it difficult to achieve a precise measurement of Betelgeuse's luminosity, but research from 2012 quotes a luminosity of around, assuming a distance of 200 pc.\nStudies since 2001 report effective temperatures ranging from 3,250 to 3,690 [K](https://bliptext.com/articles/kelvin).\nValues outside this range have previously been reported, and much of the variation is believed to be real, due to pulsations in the atmosphere.\nThe star is also a slow rotator and the most recent velocity recorded was 5.45 km/s —much slower than [Antares](https://bliptext.com/articles/antares) which has a rotational velocity of 20 km/s.\nThe rotation period depends on Betelgeuse's size and orientation to Earth, but it has been calculated to take 36 years to turn on its axis, inclined at an angle of around 60 ° to Earth.\nIn 2004, astronomers using computer simulations speculated that even if Betelgeuse is not rotating it might exhibit large-scale magnetic activity in its extended atmosphere, a factor where even moderately strong fields could have a meaningful influence over the star's dust, wind and mass-loss properties.\nA series of [spectropolarimetric](https://bliptext.com/articles/spectropolarimetry) observations obtained in 2010 with the [Bernard Lyot Telescope](https://bliptext.com/articles/bernard-lyot-telescope) at [Pic du Midi Observatory](https://bliptext.com/articles/pic-du-midi-observatory) revealed the presence of a weak magnetic field at the surface of Betelgeuse, suggesting that the giant convective motions of supergiant stars are able to trigger the onset of a small-scale [dynamo effect](https://bliptext.com/articles/dynamo-effect).\n\n## Mass\nBetelgeuse has no known orbital companions, so its mass cannot be calculated by that direct method.\nModern mass estimates from theoretical modelling have produced values of, with values of – from older studies.\nIt has been calculated that Betelgeuse began its life as a star of, based on a solar luminosity of 90,000–150,000.\nA novel method of determining the supergiant's mass was proposed in 2011, arguing for a current stellar mass of with an upper limit of 16.6 and lower of, based on observations of the star's intensity profile from narrow H-band interferometry and using a photospheric measurement of roughly 4.3 AU or.\nA probablystic age prior analysis give a current mass of and an initial mass of.\nBetelgeuse's mass can also be estimated based on its position on the [colormagnitudediagram (CMD)](https://bliptext.com/articles/hertzsprung-russell-diagram).\nBetelgeuse's color may have changed from yellow (or possibly orange; i.e. a yellow supergiant) to red in the last few thousand years, based on a 2022 review of historical records.\nThis color change combined with the CMD suggest a mass of and age of 14 Myr, and a distance from 125 to 150 parsecs (~400 to 500 light years).\n\n## Motion\nThe [kinematics](https://bliptext.com/articles/kinematics) of Betelgeuse are complex.\nThe age of Class M supergiants with an initial mass of is roughly 10 million years.\nStarting from its present position and motion, a projection back in time would place Betelgeuse around 290 parsecs farther from the [galactic plane](https://bliptext.com/articles/galactic-plane)—an implausible location, as there is no [star formation](https://bliptext.com/articles/star-formation) [region](https://bliptext.com/articles/molecular-cloud) there.\nMoreover, Betelgeuse's projected pathway does not appear to intersect with the [25 Ori](https://bliptext.com/articles/25-orionis) [subassociation](https://bliptext.com/articles/orion-ob1-association) or the far younger Orion Nebula Cluster (ONC, also known as Ori OB1d), particularly since [Very Long Baseline Array](https://bliptext.com/articles/very-long-baseline-array) astrometry yields a distance from Betelgeuse to the ONC of between 389 and 414 parsecs.\nConsequently, it is likely that Betelgeuse has not always had its current motion through space but has changed course at one time or another, possibly the result of a nearby [stellar explosion](https://bliptext.com/articles/supernova).\nAn observation by the [Herschel Space Observatory](https://bliptext.com/articles/herschel-space-observatory) in January 2013 revealed that the star's winds are crashing against the surrounding interstellar medium.\nThe most likely star-formation scenario for Betelgeuse is that it is a runaway star from the [Orion OB1 association](https://bliptext.com/articles/orion-ob1-association).\nOriginally a member of a high-mass multiple system within Ori OB1a, Betelgeuse was probably formed about 10–12 million years ago, but has evolved rapidly due to its high mass.\nH. Bouy and J. Alves suggested in 2015 that Betelgeuse may instead be a member of the newly discovered Taurion [OB association](https://bliptext.com/articles/ob-association).\n# [Map showing the Orion OB1 association, which contains the blue supergiants of Orion's Belt and the Orion Nebula. Betelgeuse is believed to be a runaway star that was ejected from the Orion OB1 association. | upload.wikimedia.org/wikipedia/commons/4/48/Orion///OB1///%26///25///Ori///Group.png]\n\n## Circumstellar dynamics\nIn the late phase of [stellar evolution](https://bliptext.com/articles/stellar-evolution), massive stars like Betelgeuse exhibit high rates of [mass loss](https://bliptext.com/articles/stellar-mass-loss), possibly as much as every 10,000 years, resulting in a complex [circumstellar environment](https://bliptext.com/articles/circumstellar-envelope) that is constantly in flux.\nIn a 2009 paper, stellar mass loss was cited as the \"key to understanding the evolution of the universe from the earliest cosmological times to the current epoch, and of planet formation and the formation of life itself\".\nHowever, the physical mechanism is not well understood.\nWhen [Martin Schwarzschild](https://bliptext.com/articles/martin-schwarzschild) first proposed his theory of huge convection cells, he argued it was the likely cause of mass loss in evolved supergiants like Betelgeuse.\nRecent work has corroborated this hypothesis, yet there are still uncertainties about the structure of their convection, the mechanism of their mass loss, the way dust forms in their extended atmosphere, and the conditions which precipitate their dramatic finale as a type II supernova.\nIn 2001, Graham Harper estimated a stellar wind at every 10,000 years, but research since 2009 has provided evidence of episodic mass loss making any total figure for Betelgeuse uncertain.\nCurrent observations suggest that a star like Betelgeuse may spend a portion of its lifetime as a [red supergiant](https://bliptext.com/articles/red-supergiant-star), but then cross back across the H–R diagram, pass once again through a brief [yellow supergiant](https://bliptext.com/articles/yellow-supergiant-star) phase and then explode as a [blue supergiant](https://bliptext.com/articles/blue-supergiant) or [Wolf–Rayet star](https://bliptext.com/articles/wolf-rayet-star).\nAstronomers may be close to solving this mystery.\nThey noticed a large plume of gas extending at least six times its stellar radius indicating that Betelgeuse is not shedding matter evenly in all directions.\nThe plume's presence implies that the spherical symmetry of the star's photosphere, often observed in the infrared, is not preserved in its close environment.\nAsymmetries on the stellar disk had been reported at different wavelengths.\nHowever, due to the refined capabilities of the [NACO](https://bliptext.com/articles/list-of-instruments-at-the-very-large-telescope) adaptive optics on the VLT, these asymmetries have come into focus.\nThe two mechanisms that could cause such asymmetrical mass loss, were large-scale convection cells or polar mass loss, possibly due to rotation.\nProbing deeper with ESO's AMBER, gas in the supergiant's extended atmosphere has been observed vigorously moving up and down, creating bubbles as large as the supergiant itself, leading his team to conclude that such stellar upheaval is behind the massive plume ejection observed by Kervella.\n# [Image from ESO's Very Large Telescope showing the stellar disk and an extended atmosphere with a previously unknown plume of surrounding gas | upload.wikimedia.org/wikipedia/commons/9/92/ESO-Betelgeuse.jpg]\n# [Artist's rendering from ESO showing Betelgeuse with a gigantic bubble boiling on its surface and a radiant plume of gas being ejected to six photospheric radii or roughly the orbit of Neptune | upload.wikimedia.org/wikipedia/commons/8/81/Betelgeuse///Plume///eso0927d.jpg]\n\n### Asymmetric shells\nIn addition to the photosphere, six other components of Betelgeuse's atmosphere have now been identified.\nThey are a molecular environment otherwise known as the MOLsphere, a gaseous envelope, a chromosphere, a dust environment and two outer shells (S1 and S2) composed of [carbon monoxide](https://bliptext.com/articles/carbon-monoxide) (CO).\nSome of these elements are known to be asymmetric while others overlap.\nAt about 0.45 stellar radii (~2–3 AU) above the photosphere, there may lie a molecular layer known as the MOLsphere or molecular environment.\nStudies show it to be composed of water vapor and carbon monoxide with an effective temperature of about 1,500 K. Water vapor had been originally detected in the supergiant's spectrum in the 1960s with the two Stratoscope projects but had been ignored for decades.\nThe MOLsphere may also contain [SiO](https://bliptext.com/articles/silicon-monoxide) and [Al2O3](https://bliptext.com/articles/aluminium-oxide)—molecules which could explain the formation of dust particles.\nAnother cooler region, the asymmetric gaseous envelope, extends for several radii (~10–40 AU) from the photosphere.\nIt is enriched in oxygen and especially in [nitrogen](https://bliptext.com/articles/nitrogen) relative to carbon.\nThese composition anomalies are likely caused by contamination by [CNO](https://bliptext.com/articles/cno-cycle)-processed material from the inside of Betelgeuse.\nRadio-telescope images taken in 1998 confirm that Betelgeuse has a highly complex atmosphere, with a temperature of 3,450 K, similar to that recorded on the star's surface but much lower than surrounding gas in the same region.\nThe VLA images also show this lower-temperature gas progressively cools as it extends outward.\nAlthough unexpected, it turns out to be the most abundant constituent of Betelgeuse's atmosphere.\n\"This alters our basic understanding of red-supergiant star atmospheres\", explained Jeremy Lim, the team's leader.\n\"Instead of the star's atmosphere expanding uniformly due to gas heated to high temperatures near its surface, it now appears that several giant convection cells propel gas from the star's surface into its atmosphere.\"\nThis is the same region in which Kervella's 2009 finding of a bright plume, possibly containing carbon and nitrogen and extending at least six photospheric radii in the southwest direction of the star, is believed to exist.\nThe [chromosphere](https://bliptext.com/articles/chromosphere) was directly imaged by the Faint Object Camera on board the Hubble Space Telescope in ultraviolet wavelengths.\nThe images also revealed a bright area in the southwest quadrant of the disk.\nThe average radius of the chromosphere in 1996 was about 2.2 times the optical disk (~10 AU) and was reported to have a temperature no higher than 5,500 K. However, in 2004 observations with the STIS, Hubble's high-precision spectrometer, pointed to the existence of warm chromospheric plasma at least one arcsecond away from the star.\nAt a distance of 197 pc, the size of the chromosphere could be up to 200 AU.\nThe observations have conclusively demonstrated that the warm chromospheric plasma spatially overlaps and co-exists with cool gas in Betelgeuse's gaseous envelope as well as with the dust in its circumstellar dust shells.\nThe first claim of a dust shell surrounding Betelgeuse was put forth in 1977 when it was noted that dust shells around mature stars often emit large amounts of radiation in excess of the photospheric contribution.\nUsing [heterodyne interferometry](https://bliptext.com/articles/interferometry), it was concluded that the red supergiant emits most of its excess radiation from positions beyond 12 stellar radii or roughly the distance of the [Kuiper belt](https://bliptext.com/articles/kuiper-belt) at 50 to 60 AU, which depends on the assumed stellar radius.\nSince then, there have been studies done of this dust envelope at varying wavelengths yielding decidedly different results.\nStudies from the 1990s have estimated the inner radius of the dust shell anywhere from 0.5 to 1 arcseconds, or 100 to 200 AU.\nThese studies point out that the dust environment surrounding Betelgeuse is not static.\nIn 1994, it was reported that Betelgeuse undergoes sporadic decades-long dust production, followed by inactivity.\nIn 1997, significant changes in the dust shell's morphology in one year were noted, suggesting that the shell is asymmetrically illuminated by a stellar radiation field strongly affected by the existence of photospheric hotspots.\nThe 1984 report of a giant asymmetric dust shell 1 pc (206,265 AU) has not been corroborated by recent studies, although another published the same year said that three dust shells were found extending four light-years from one side of the decaying star, suggesting that Betelgeuse sheds its outer layers as it moves.\nAlthough the exact size of the two outer [CO](https://bliptext.com/articles/carbon-monoxide) shells remains elusive, preliminary estimates suggest that one shell extends from about 1.5 to 4.0 [arcseconds](https://bliptext.com/articles/arcseconds) and the other expands as far as 7.0 [arcseconds](https://bliptext.com/articles/arcseconds).\nAssuming the Jovian orbit of 5.5 AU as the star radius, the inner shell would extend roughly 50 to 150 stellar radii (~300 to 800 AU) with the outer one as far as 250 stellar radii (~1,400 AU).\nThe Sun's [heliopause](https://bliptext.com/articles/heliopause-astronomy) is estimated at 100 AU, so the size of this outer shell would be almost fourteen times the size of the Solar System.\n# [Exterior view of ESO's Very Large Telescope (VLT) in Paranal, Chile | upload.wikimedia.org/wikipedia/commons/4/4b/ESO///Paranal///Platform.jpg]\n# [Interior view of one of the four 8.2-meter Unit Telescopes at ESO's VLT | upload.wikimedia.org/wikipedia/commons/9/97/Eso-paranal-16.jpg]\n# [This infrared image from the ESO's VLT shows complex shells of gas and dust around Betelgeuse – the tiny red circle in the middle is the size of the photosphere. | upload.wikimedia.org/wikipedia/commons/a/a0/Nebula///around///Betelgeuse.jpg]\n\n### Supersonic bow shock\nBetelgeuse is travelling through the interstellar medium at a speed of 30 km/second (i.e. ~6.3 AU/year) creating a [bow shock](https://bliptext.com/articles/bow-shocks-in-astrophysics).\nThe shock is not created by the star, but by its powerful [stellar wind](https://bliptext.com/articles/stellar-wind) as it ejects vast amounts of gas into the interstellar medium at a speed of 17 km/s, heating the material surrounding the star, thereby making it visible in infrared light.\nBecause Betelgeuse is so bright, it was only in 1997 that the bow shock was first imaged.\nThe [cometary](https://bliptext.com/articles/comet) structure is estimated to be at least one parsec wide, assuming a distance of 643 light-years.\n[Hydrodynamic](https://bliptext.com/articles/fluid-dynamics) simulations of the bow shock made in 2012 indicate that it is very young—less than 30,000 years old—suggesting two possibilities: that Betelgeuse moved into a region of the interstellar medium with different properties only recently or that Betelgeuse has undergone a significant transformation producing a changed stellar wind.\nA 2012 paper, proposed that this phenomenon was caused by Betelgeuse transitioning from a [blue supergiant](https://bliptext.com/articles/blue-supergiant) (BSG) to a red supergiant (RSG).\nThere is evidence that in the late evolutionary stage of a star like Betelgeuse, such stars \"may undergo rapid transitions from red to blue and vice versa on the Hertzsprung–Russell diagram, with accompanying rapid changes to their stellar winds and bow shocks.\"\nMoreover, if future research bears out this hypothesis, Betelgeuse may prove to have traveled close to 200,000 AU as a red supergiant scattering as much as 3 M_solar along its trajectory.\n\n# Life phases\nBetelgeuse is a red supergiant that has evolved from an [O-type main-sequence star](https://bliptext.com/articles/o-type-main-sequence-star).\nAfter core hydrogen exhaustion, Betelgeuse evolved into a blue supergiant before evolving into its current red supergiant form.\nIts core will eventually collapse, producing a [supernova](https://bliptext.com/articles/supernova) explosion and leaving behind a compact [remnant](https://bliptext.com/articles/supernova-remnant).\nThe details depend on the exact initial mass and other physical properties of that main sequence star.\n\n## Main sequence\nThe initial mass of Betelgeuse can only be estimated by testing different stellar evolutionary models to match its current observed properties.\nThe unknowns of both the models and the current properties mean that there is considerable uncertainty in Betelgeuse's initial appearance, but its mass is usually estimated to have been in the range of, with modern models finding values of.\nIts chemical makeup can be reasonably assumed to have been around 70% hydrogen, 28% helium, and 2.4% heavy elements, slightly more metal-rich than the Sun but otherwise similar.\nThe initial rotation rate is more uncertain, but models with slow to moderate initial rotation rates produce the best matches to Betelgeuse's current properties.\nThat main sequence version of Betelgeuse would have been a hot luminous star with a spectral type such as O9V.\nA star would take between 11.5 and 15 million years to reach the red supergiant stage, with more rapidly-rotating stars taking the longest.\nRapidly-rotating stars take 9.3 million years to reach the red supergiant stage, while stars with slow rotation take only 8.1 million years.\nThese are the best estimates of Betelgeuse's current age, as the time since its [zero age main sequence](https://bliptext.com/articles/main-sequence) stage is estimated to be 8.0–8.5 million years as a star with no rotation.\n# [Hertzsprung–Russell diagram identifying supergiants like Betelgeuse that have moved off the main sequence | upload.wikimedia.org/wikipedia/commons/9/96/Hertzsprung-Russell///Diagram///-///ESO.png]\n\n## After core hydrogen exhaustion\nBetelgeuse's time spent as a red supergiant can be estimated by comparing mass loss rates to the observed circumstellar material, as well as the abundances of heavy elements at the surface.\nEstimates range from 10,000 years to a maximum of 140,000 years.\nBetelgeuse appears to undergo short periods of heavy mass loss and is a runaway star moving rapidly through space, so comparisons of its current mass loss to the total lost mass are difficult.\nThe surface of Betelgeuse shows enhancement of nitrogen, relatively low levels of carbon, and a high proportion of [13C](https://bliptext.com/articles/carbon-13) relative to [12C](https://bliptext.com/articles/carbon-12), all indicative of a star that has experienced the [first dredge-up](https://bliptext.com/articles/dredge-up).\nHowever, the first dredge-up occurs soon after a star reaches the red supergiant phase and so this only means that Betelgeuse has been a red supergiant for at least a few thousand years.\nThe best prediction is that Betelgeuse has already spent around 40,000 years as a red supergiant, having left the main sequence perhaps one million years ago.\nThe current mass can be estimated from evolutionary models from the initial mass and the expected mass lost so far.\nFor Betelgeuse, the total mass lost is predicted to be no more than about, giving a current mass of , considerably higher than estimated by other means such as pulsational properties or limb-darkening models.\nAll stars more massive than about are expected to end their lives when their cores collapse, typically producing a supernova explosion.\nUp to about, a type II-P supernova is always produced from the red supergiant stage.\nMore massive stars can lose mass quickly enough that they evolve towards higher temperatures before their cores can collapse, particularly for rotating stars and models with especially high mass loss rates.\nThese stars can produce type II-L or type IIb supernovae from yellow or blue supergiants, or type I b/c supernovae from Wolf–Rayet stars.\nModels of rotating stars predict a peculiar type II supernova similar to [SN 1987A](https://bliptext.com/articles/sn-1987a) from a [blue supergiant](https://bliptext.com/articles/blue-supergiant) progenitor.\nOn the other hand, non-rotating models predict a type II-P supernova from a red [supergiant](https://bliptext.com/articles/supergiant) progenitor.\nThe time until Betelgeuse explodes depends on the predicted initial conditions and on the estimate of the time already spent as a red supergiant.\nThe total lifetime from the start of the red supergiant phase to core collapse varies from about 300,000 years for a rotating star, 550,000 years for a rotating star, and up to a million years for a non-rotating star.\nGiven the estimated time since Betelgeuse became a red supergiant, estimates of its remaining lifetime range from a \"best guess\" of under 100,000 years for a non-rotating model to far longer for rotating models or lower-mass stars.\nBetelgeuse's suspected birthplace in the [Orion OB1 association](https://bliptext.com/articles/orion-ob1-association) is the location of several previous supernovae.\nIt is believed that runaway stars may be caused by supernovae, and there is strong evidence that [OB stars](https://bliptext.com/articles/ob-star) [μ Columbae](https://bliptext.com/articles/mu-columbae), [AE Aurigae](https://bliptext.com/articles/ae-aurigae), and [53 Arietis](https://bliptext.com/articles/53-arietis) all originated from such explosions in Ori OB1 2.2, 2.7, and 4.9 million years ago.\nA typical type II-P [supernova](https://bliptext.com/articles/supernova) emits 2 J of [neutrinos](https://bliptext.com/articles/neutrino) and produces an explosion with a kinetic energy of 2 J. As seen from Earth, Betelgeuse as a type IIP [supernova](https://bliptext.com/articles/supernova) would have a peak apparent magnitude somewhere in the range −8 to −12.\nThis would be easily visible in daylight, with a possible brightness up to a significant fraction of the [full moon](https://bliptext.com/articles/full-moon), though likely not exceeding it.\nThis type of supernova would remain at roughly constant brightness for 2–3 months before rapidly dimming.\nThe visible light is produced mainly by the radioactive decay of [cobalt](https://bliptext.com/articles/cobalt), and sustains its brightness due to the increasing transparency of the cooling hydrogen ejected by the supernova.\n# [This is what Betelgeuse may have looked like up until about 1 million years ago, when it was a main-sequence star. | upload.wikimedia.org/wikipedia/commons/f/fc/O-type///star.png]\n# [Celestia depiction of Orion as it might appear from Earth when Betelgeuse explodes as a supernova, which could be brighter than the supernova that exploded in 1006 (SN 1006) | upload.wikimedia.org/wikipedia/commons/5/57/Betelgeuse///supernova.png]\n\n### Media reporting\nDue to misunderstandings caused by the 2009 publication of the star's 15% contraction, apparently of its outer atmosphere, Betelgeuse has frequently been the subject of scare stories and rumors suggesting that it will explode within a year, and leading to exaggerated claims about the consequences of such an event.\nThe timing and prevalence of these rumors have been linked to broader misconceptions of astronomy, particularly to doomsday predictions relating to the [Mayan calendrical apocalypse](https://bliptext.com/articles/2012-phenomenon).\nBetelgeuse is not likely to produce a [gamma-ray burst](https://bliptext.com/articles/gamma-ray-burst) and is not close enough for its [X-rays](https://bliptext.com/articles/x-ray), ultraviolet radiation, or ejected material to cause significant effects on [Earth](https://bliptext.com/articles/earth).\nFollowing the dimming of Betelgeuse in December 2019, reports appeared in the science and mainstream media that again included speculation that the star might be about to explode as a supernova – even in the face of scientific research that a supernova is not expected for perhaps 100,000 years.\nSome outlets reported the magnitude as faint as +1.3 as an unusual and interesting phenomenon, like Astronomy magazine, the [National Geographic](https://bliptext.com/articles/national-geographic), and the Smithsonian.\nSome mainstream media, like [The Washington Post](https://bliptext.com/articles/the-washington-post), [ABC News](https://bliptext.com/articles/abc-news-australia) in Australia, and [Popular Science](https://bliptext.com/articles/popular-science), reported that a supernova was possible but unlikely, whilst other outlets falsely portrayed a supernova as an imminent realistic possibility.\n[CNN](https://bliptext.com/articles/cnn), for example, chose the headline \"A giant red star is acting weird and scientists think it may be about to explode\", while the [New York Post](https://bliptext.com/articles/new-york-post) declared Betelgeuse as \"due for explosive supernova\".\n[Phil Plait](https://bliptext.com/articles/phil-plait), in his [Bad Astronomy](https://bliptext.com/articles/bad-astronomy) blog, noting that Betelgeuse's recent behaviour, \"[w]hile unusual . . . isn't unprecedented,\" argued that the star is not likely to explode \"for a long, long time.\"\n[Dennis Overbye](https://bliptext.com/articles/dennis-overbye) of [The New York Times](https://bliptext.com/articles/the-new-york-times) agreed that an explosion was not imminent but added that \"astronomers are having fun thinking about it.\"\nFollowing the eventual supernova, [a small dense remnant](https://bliptext.com/articles/compact-star) will be left behind, either a [neutron star](https://bliptext.com/articles/neutron-star) or [black hole](https://bliptext.com/articles/black-hole).\nBetelgeuse does not seem to have a core massive enough for a black hole, so the remnant will probably be a neutron star of approximately.\n\n# Ethnological attributes\n\n## Spelling and pronunciation\nBetelgeuse has also been spelled Betelgeux and, in [German](https://bliptext.com/articles/german-language), Beteigeuze (according to [Bode](https://bliptext.com/articles/johann-elert-bode)).\nBetelgeux and Betelgeuze were used until the early 20th century, when the spelling Betelgeuse became universal.\nConsensus on its pronunciation is weak and is as varied as its spellings:\nThe -urz pronunciations are attempts to render the French eu sound; they only work in r-dropping accents.\n\n## Etymology\nBetelgeuse is often mistranslated as \"armpit of the central one\".\nIn his 1899 work [Star-Names and Their Meanings](https://bliptext.com/articles/star-names), American amateur naturalist Richard Hinckley Allen stated the derivation was from the ابط الجوزاء , which he claimed degenerated into a number of forms, including Bed Elgueze, Beit Algueze, Bet El-gueze, and Beteigeuze, to the forms Betelgeuse, Betelguese, Betelgueze and Betelgeux.\nThe star was named Beldengeuze in the [Alfonsine Tables](https://bliptext.com/articles/alfonsine-tables), and Italian [Jesuit](https://bliptext.com/articles/jesuit) priest and astronomer [Giovanni Battista Riccioli](https://bliptext.com/articles/giovanni-battista-riccioli) had called it Bectelgeuze or Bedalgeuze.\nPaul Kunitzsch, Professor of Arabic Studies at the University of Munich, refuted Allen's derivation and instead proposed that the full name is a corruption of the Arabic يد الجوزاء , meaning \"the Hand of al-Jauzā '\" ; i.e., Orion.\nEuropean mistransliteration into [medieval Latin](https://bliptext.com/articles/medieval-latin) led to the first character y (**ﻴ**, with two dots underneath) being misread as a b (**ﺒ**, with only one dot underneath).\nDuring the [Renaissance](https://bliptext.com/articles/renaissance), the star's name was written as بيت الجوزاء **' (\"house of Orion\") or بط الجوزاء '**, incorrectly thought to mean \"armpit of Orion\" (a true translation of \"armpit\" would be ابط, transliterated as ).\nThis led to the modern rendering as Betelgeuse.\nOther writers have since accepted Kunitzsch's explanation.\nThe last part of the name, \"-elgeuse\", comes from the Arabic الجوزاء , a historical Arabic name of the constellation [Orion](https://bliptext.com/articles/orion-constellation), a feminine name in old [Arabian legend](https://bliptext.com/articles/arabian-legend), and of uncertain meaning.\nBecause جوز **', the [root](https://bliptext.com/articles/root-linguistics) of '**, means \"middle\", roughly means \"the Central One\".\nThe modern Arabic name for Orion is الجبار **' (\"the Giant\"), although the use of الجوزاء '** in the star's name has continued.\nThe 17th-century English translator [Edmund Chilmead](https://bliptext.com/articles/edmund-chilmead) gave it the name Ied Algeuze (\"Orion's Hand\"), from [Christmannus](https://bliptext.com/articles/jakob-christmann).\nOther Arabic names recorded include اليد اليمنى **' (\"the Right Hand\"), الذراع '** (\"the Arm\"), and المنكب **' (\"the Shoulder\"), all of al-Jauzā, Orion, as منكب الجوزاء '**.\n# [An illustration of Orion (horizontally reversed) in al-Sufi's Book of Fixed Stars. Betelgeuze is annotated as Yad al-Jauzā (\"Hand of Orion\"), one of the proposed etymological origins of its modern name, and also as Mankib al Jauzā' (\"Shoulder of Orion\"). | upload.wikimedia.org/wikipedia/commons/b/bd/Al-Sufi%27s///Orion%2C///1125///Baghdad///copy%2C///Doha///Museum///of///Islamic///Art///Ms///2.///1998.///SO.jpg]\n# [Dunhuang Star Chart, circa AD 700, showing 參宿四 Shēnxiùsì (Betelgeuse), the Fourth Star of the constellation of Three Stars | upload.wikimedia.org/wikipedia/commons/9/95/Dunhuang///Star///Atlas///-///Orion.jpg]\n\n## Other names\nOther names for Betelgeuse included the Persian Bašn \"the Arm\", and [Coptic](https://bliptext.com/articles/coptic-language) Klaria \"an Armlet\".\nBahu was its [Sanskrit](https://bliptext.com/articles/sanskrit) name, as part of a Hindu understanding of the constellation as a running antelope or stag.\nIn traditional [Chinese astronomy](https://bliptext.com/articles/chinese-astronomy), the [name](https://bliptext.com/articles/chinese-star-names) for Betelgeuse is 参宿四 (Shēnxiùsì, the Fourth Star of the constellation of [Three Stars](https://bliptext.com/articles/three-stars-chinese-constellation)) as the [Chinese constellation](https://bliptext.com/articles/orion-in-chinese-astronomy) 参宿 originally referred to the three stars in [Orion's Belt](https://bliptext.com/articles/orion-s-belt).\nThis constellation was ultimately expanded to ten stars, but the earlier name stuck.\nIn Japan, the [Taira, or Heike, clan](https://bliptext.com/articles/heike-clan) adopted Betelgeuse and its red color as its symbol, calling the star Heike-boshi, (平家星), while the [Minamoto, or Genji, clan](https://bliptext.com/articles/minamoto-clan) chose Rigel and its white color.\nThe two powerful families fought a [legendary war](https://bliptext.com/articles/genpei-war) in Japanese history, the stars seen as facing each other off and only kept apart by the Belt.\nIn Tahitian lore, Betelgeuse was one of the pillars propping up the sky, known as Anâ-varu, the pillar to sit by.\nIt was also called Ta'urua-nui-o-Mere \"Great festivity in parental yearnings\".\nA Hawaiian term for it was Kaulua-koko (\"brilliant red star\").\nThe [Lacandon people](https://bliptext.com/articles/lacandon-people) of Central America knew it as chäk tulix (\"red butterfly\").\nAstronomy writer [Robert Burnham Jr.](https://bliptext.com/articles/robert-burnham-jr) proposed the term padparadaschah, which denotes a rare orange sapphire in India, for the star.\n\n## Mythology\nWith the [history of astronomy](https://bliptext.com/articles/history-of-astronomy) intimately associated with mythology and astrology before the [scientific revolution](https://bliptext.com/articles/scientific-revolution), the red star, like the planet Mars that derives its name from a [Roman war god](https://bliptext.com/articles/mars-mythology), has been closely associated with the martial [archetype](https://bliptext.com/articles/archetype) of conquest for millennia, and by extension, the motif of death and rebirth.\nOther cultures have produced different myths.\nStephen R. Wilk has proposed the constellation of Orion could have represented the Greek mythological figure [Pelops](https://bliptext.com/articles/pelops), who had an artificial shoulder of ivory made for him, with Betelgeuse as the shoulder, its color reminiscent of the reddish yellow sheen of ivory.\n[Aboriginal](https://bliptext.com/articles/australian-aborigines) people from the [Great Victoria Desert](https://bliptext.com/articles/great-victoria-desert) of South Australia incorporated Betelgeuse into their oral traditions as the club of Nyeeruna (Orion), which fills with fire-magic and dissipates before returning.\nThis has been interpreted as showing that early Aboriginal observers were aware of the brightness variations of Betelgeuse.\nThe [Wardaman people](https://bliptext.com/articles/wardaman-people) of northern Australia knew the star as Ya-jungin (\"Owl Eyes Flicking\"), its variable light signifying its intermittent watching of ceremonies led by the Red Kangaroo Leader Rigel.\nIn South African mythology, Betelgeuse was perceived as a lion casting a predatory gaze toward the three zebras represented by Orion's Belt.\nIn the Americas, Betelgeuse signifies a severed limb of a man-figure (Orion)—the [Taulipang](https://bliptext.com/articles/pemon-people) of Brazil know the constellation as Zililkawai, a hero whose leg was cut off by his wife, with the variable light of Betelgeuse linked to the severing of the limb.\nSimilarly, the [Lakota people](https://bliptext.com/articles/lakota-people) of North America see it as a chief whose arm has been severed.\nA Sanskrit name for Betelgeuse is ārdrā (\"the moist one\"), eponymous of the [Ardra](https://bliptext.com/articles/ardra-nakshatra) [lunar mansion](https://bliptext.com/articles/nakshatra) in [Hindu astrology](https://bliptext.com/articles/hindu-astrology).\nThe [Rigvedic God](https://bliptext.com/articles/rigvedic-deities) of storms [Rudra](https://bliptext.com/articles/rudra) presided over the star; this association was linked by 19th-century star enthusiast [Richard Hinckley Allen](https://bliptext.com/articles/star-names-their-lore-and-meaning) to Orion's stormy nature.\nThe constellations in Macedonian folklore represented agricultural items and animals, reflecting their way of life.\nTo them, Betelgeuse was Orach (\"the ploughman\"), alongside the rest of Orion, which depicted a plough with oxen.\nThe rising of Betelgeuse at around 3 a.m. in late summer and autumn signified the time for village men to go to the fields and plough.\nTo the [Inuit](https://bliptext.com/articles/inuit-astronomy), the appearance of Betelgeuse and [Bellatrix](https://bliptext.com/articles/bellatrix) high in the southern sky after sunset marked the beginning of spring and lengthening days in late February and early March.\nThe two stars were known as Akuttujuuk (\"those [two] placed far apart\"), referring to the distance between them, mainly to people from North Baffin Island and Melville Peninsula.\nThe opposed locations of Orion and [Scorpius](https://bliptext.com/articles/scorpius), with their corresponding bright red variable stars Betelgeuse and [Antares](https://bliptext.com/articles/antares), were noted by ancient cultures around the world.\nThe setting of Orion and rising of Scorpius signify the death of Orion by the scorpion.\nIn China they signify brothers and rivals Shen and Shang.\nThe [Batak](https://bliptext.com/articles/batak-indonesia) of Sumatra marked their New Year with the first [new moon](https://bliptext.com/articles/new-moon) after the sinking of Orion's Belt below the horizon, at which point Betelgeuse remained \"like the tail of a rooster\".\nThe positions of Betelgeuse and Antares at opposite ends of the celestial sky were considered significant, and their constellations were seen as a pair of scorpions.\nScorpion days marked as nights that both constellations could be seen.\n\n## In popular culture\nAs one of the brightest and best-known stars, Betelgeuse has featured in many works of fiction.\nThe star's unusual name inspired the title of the 1988 film [Beetlejuice](https://bliptext.com/articles/beetlejuice), referring to its titular antagonist, and script writer [Michael McDowell](https://bliptext.com/articles/michael-mcdowell-author) was impressed by how many people made the connection.\nIn the popular science fiction series [The Hitchhiker's Guide to the Galaxy](https://bliptext.com/articles/the-hitchhiker-s-guide-to-the-galaxy) by [Douglas Adams](https://bliptext.com/articles/douglas-adams), [Ford Prefect](https://bliptext.com/articles/ford-prefect-character) was from \"a small planet somewhere in the vicinity of Betelgeuse.\"\nTwo American navy ships were named after the star, both of them World War II vessels, the USS Betelgeuse (AKA-11) launched in 1939 and USS Betelgeuse (AK-260) launched in 1944.\nIn 1979, the French supertanker [Betelgeuse](https://bliptext.com/articles/whiddy-island-disaster) was moored off [Whiddy Island](https://bliptext.com/articles/whiddy-island), discharging oil when it exploded, killing 50 people in one of the worst disasters in Ireland's history.\nThe [Dave Matthews Band](https://bliptext.com/articles/dave-matthews-band) song \"[Black and Blue Bird](https://bliptext.com/articles/black-and-blue-bird-song)\" references the star.\nThe [Blur](https://bliptext.com/articles/blur-band) song \"Far Out\" from their 1994 album [Parklife](https://bliptext.com/articles/parklife) mentions Betelgeuse in its lyrics.\nThe [Philip Larkin](https://bliptext.com/articles/philip-larkin) poem \"The North Ship\", found in [the collection of the same name](https://bliptext.com/articles/the-north-ship), references the star in the section \"Above 80° N\", which reads: \" 'A woman has ten claws,' / Sang the drunken boatswain; / Farther than Betelgeuse, / More brilliant than Orion / Or the planets Venus and Mars, / The star flames on the ocean; / 'A woman has ten claws,' / Sang the drunken boatswain.\"\n[Humbert Wolfe](https://bliptext.com/articles/humbert-wolfe) wrote a poem about Betelgeuse, which was set to music by [Gustav Holst](https://bliptext.com/articles/gustav-holst).\n\n# Table of angular diameter estimates\nThis table provides a non-exhaustive list of angular measurements conducted since 1920.\nAlso included is a column providing a current range of radii for each study based on Betelgeuse's most recent distance estimate (Harper et al.) of 197 pc.","current_revision":"b9a33064-1402-4fcc-b218-77eec406e351","created_by":"kACnuQmH5k9Nr5VNVEpVeg7XpvUmMctD","created_at":"2025-01-25T17:38:44.946Z","updated_at":"2025-03-21T17:57:13.708Z","search_vector":"'betelgeus':1","search_content":" \n \n\n# \n**Betelgeuse** is a [red supergiant](https://bliptext.com/articles/red-supergiant) star in the [constellation](https://bliptext.com/articles/constellation) of [Orion](https://bliptext.com/articles/orion-constellation).\nIt is usually the [tenth-brightest](https://bliptext.com/articles/list-of-brightest-[star](https://bliptext.com/articles/star)s) [star](https://bliptext.com/articles/star) in the [night sky](https://bliptext.com/articles/night-sky) and, after [Rigel](https://bliptext.com/articles/rigel), the second-brightest in its constellation.\nIt is a distinctly reddish, [semiregular variable star](https://bliptext.com/articles/semiregular-variable-star) whose [apparent magnitude](https://bliptext.com/articles/apparent-magnitude), varying between +0.0 and +1.6, has the widest range displayed by any [first-magnitude star](https://bliptext.com/articles/first-magnitude-star).\nBetelgeuse is the brightest star in the night sky at [near-infrared](https://bliptext.com/articles/near-infrared) wavelengths.\nIts [Bayer designation](https://bliptext.com/articles/bayer-designation) is ****α Ori**onis**, [Latinised](https://bliptext.com/articles/latinisation-of-names) to ****Alpha Ori**onis** and abbreviated **Alpha Ori** or **α Ori**.\nWith a radius between 640 and 764 times that of the Sun, if it were at the center of our [Solar System](https://bliptext.com/articles/solar-system), its surface would lie beyond the [asteroid belt](https://bliptext.com/articles/asteroid-belt) and it would engulf the [orbits](https://bliptext.com/articles/orbit) of [Mercury](https://bliptext.com/articles/mercury-planet), [Venus](https://bliptext.com/articles/venus), [Earth](https://bliptext.com/articles/earth), and [Mars](https://bliptext.com/articles/mars).\nCalculations of Betelgeuse's mass range from slightly under ten to a little over twenty times that of the [Sun](https://bliptext.com/articles/sun).\nFor [various reasons](https://bliptext.com/articles/), its distance has been quite difficult to measure; current best estimates are of the order of 400–600 [light-years](https://bliptext.com/articles/light-year) from the Sun – a comparatively wide uncertainty for a relatively nearby star.\nIts [absolute magnitude](https://bliptext.com/articles/absolute-magnitude) is about −6.\nWith an age of less than 10 million years, Betelgeuse has evolved rapidly because of its large mass, and is expected to end its evolution with a [supernova](https://bliptext.com/articles/supernova) explosion, most likely within 100,000 years.\nWhen Betelgeuse explodes, it will shine as bright as the [half-Moon](https://bliptext.com/articles/lunar-phase) for more than three months; life on Earth will be unharmed.\nHaving been ejected from its birthplace in the [Orion OB1 association](https://bliptext.com/articles/orion-ob1-association) – which includes the stars in [Orion's Belt](https://bliptext.com/articles/orion-s-belt) – this [runaway star](https://bliptext.com/articles/runaway-star) has been observed to be moving through the [interstellar medium](https://bliptext.com/articles/interstellar-medium) at a speed of 30 km/s, creating a [bow shock](https://bliptext.com/articles/bow-shocks-in-astrophysics) over four light-years wide.\nBetelgeuse became the first extrasolar star whose [photosphere](https://bliptext.com/articles/photosphere)'s angular size was measured in 1920, and subsequent studies have reported an [angular diameter](https://bliptext.com/articles/angular-diameter) (i.e., apparent size) ranging from 0.042 to 0.056 [arcseconds](https://bliptext.com/articles/minute-of-arc); that range of determinations is ascribed to non-sphericity, [limb darkening](https://bliptext.com/articles/limb-darkening), [pulsations](https://bliptext.com/articles/stellar-pulsations) and varying appearance at different [wavelengths](https://bliptext.com/articles/electromagnetic-radiation).\nIt is also surrounded by a complex, asymmetric [envelope](https://bliptext.com/articles/circumstellar-envelope), roughly 250 times the size of the star, caused by [mass loss](https://bliptext.com/articles/stellar-mass-loss) from the star itself.\nThe Earth-observed angular diameter of Betelgeuse is exceeded only by those of [R Doradus](https://bliptext.com/articles/r-doradus) and the Sun.\nStarting in October 2019, Betelgeuse began to dim noticeably, and by mid-February 2020 its brightness had dropped by a factor of approximately 3, from magnitude 0.5 to 1.7.\nIt then returned to a more normal brightness range, reaching a peak of 0.0 visual and 0.1 V-band magnitude in April 2023.\nInfrared observations found no significant change in [luminosity](https://bliptext.com/articles/bolometric-luminosity) over the last 50 years, suggesting that the dimming was due to a change in [extinction](https://bliptext.com/articles/extinction-astronomy) around the star rather than a more fundamental change.\nA study using the [Hubble Space Telescope](https://bliptext.com/articles/hubble-space-telescope) suggests that occluding dust was created by a surface mass ejection; this material was cast millions of miles from the star, and then cooled to form the dust that caused the dimming.\n\n# Nomenclature\nThe star's [designation](https://bliptext.com/articles/bayer-designation) is α Orionis (Latinised to Alpha Orionis), given by [Johann Bayer](https://bliptext.com/articles/johann-bayer) in 1603.\nThe traditional name Betelgeuse was derived from the [Arabic](https://bliptext.com/articles/arabic-language) يد الجوزاء \"the hand of al-Jawzā’ [i.e. Orion]\".\nAn error in the 13th-century reading of the Arabic initial [ي|yā’](https://bliptext.com/articles/y) (يـ) as [ب|bā’](https://bliptext.com/articles/b) (بـ—a difference in [i‘jām](https://bliptext.com/articles/arabic-diacritics)) led to the European name.\nIn English, there are four common pronunciations of this name, depending on whether the first e is pronounced short or long and whether the s is pronounced or :\nIn 2016, the [International Astronomical Union](https://bliptext.com/articles/international-astronomical-union) organized a [Working Group on Star Names](https://bliptext.com/articles/iau-working-group-on-star-names) (WGSN) to catalog and standardize proper names for stars.\nThe WGSN's first bulletin, issued July 2016, included a table of the first two batches of names approved by the WGSN, which included Betelgeuse for this star.\nIt is now so entered in the [IAU Catalog of Star Names](https://bliptext.com/articles/iau-working-group-on-star-names).\n\n# Observational history\nBetelgeuse and its red coloration have been noted since [antiquity](https://bliptext.com/articles/classical-antiquity); the classical astronomer [Ptolemy](https://bliptext.com/articles/ptolemy) described its color as ὑπόκιρρος (hypókirrhos = more or less orange-tawny), a term later described by a translator of [Ulugh Beg](https://bliptext.com/articles/ulugh-beg)'s [Zij-i Sultani](https://bliptext.com/articles/zij-i-sultani) as rubedo, [Latin](https://bliptext.com/articles/latin) for \"ruddiness\".\nIn the 19th century, before modern systems of [stellar classification](https://bliptext.com/articles/stellar-classification), [Angelo Secchi](https://bliptext.com/articles/angelo-secchi) included Betelgeuse as one of the prototypes for his [Class III](https://bliptext.com/articles/secchi-classes) (orange to red) stars.\nThree centuries before Ptolemy, in contrast, Chinese astronomers observed Betelgeuse as yellow; Such an observation, if accurate, could suggest the star was in a [yellow supergiant](https://bliptext.com/articles/yellow-supergiant) phase around this time, a credible possibility, given current research into these stars' complex circumstellar environment.\n\n## Nascent discoveries\nAboriginal groups in South Australia have shared oral tales of the variable brightness of Betelgeuse for at least 1,000 years.\nThe variation in Betelgeuse's brightness was described in 1836 by [Sir John Herschel](https://bliptext.com/articles/john-herschel) in Outlines of Astronomy.\nFrom 1836 to 1840, he noticed significant changes in magnitude when Betelgeuse outshone [Rigel](https://bliptext.com/articles/rigel) in October 1837 and again in November 1839.\nA 10-year quiescent period followed; then in 1849, Herschel noted another short cycle of variability, which peaked in 1852.\nLater observers recorded unusually high [maxima](https://bliptext.com/articles/maxima-and-minima) with an interval of years, but only small variations from 1957 to 1967.\nThe records of the [American Association of Variable Star Observers](https://bliptext.com/articles/american-association-of-variable-star-observers) (AAVSO) show a maximum [brightness](https://bliptext.com/articles/apparent-magnitude) of 0.2 in 1933 and 1942, and a minimum of 1.2, observed in 1927 and 1941.\nThis variability in brightness may explain why [Johann Bayer](https://bliptext.com/articles/johann-bayer), with the publication of his [Uranometria](https://bliptext.com/articles/uranometria) in 1603, designated the star alpha, as it probably rivaled the usually brighter Rigel (beta).\nFrom Arctic latitudes, Betelgeuse's red colour and higher location in the sky than Rigel meant the [Inuit](https://bliptext.com/articles/inuit) regarded it as brighter, and one local name was Ulluriajjuaq (\"large star\").\nIn 1920, [Albert A. Michelson](https://bliptext.com/articles/albert-a-michelson) and [Francis G. Pease](https://bliptext.com/articles/francis-g-pease) mounted a six-meter [interferometer](https://bliptext.com/articles/interferometry) on the front of the 2.5-meter telescope at [Mount Wilson Observatory](https://bliptext.com/articles/mount-wilson-observatory), helped by [John August Anderson](https://bliptext.com/articles/john-august-anderson).\nThe trio measured the angular diameter of Betelgeuse at 0.047[″](https://bliptext.com/articles/arcsecond), a figure that resulted in a diameter of 3.84 km (2.58 AU) based on the [parallax](https://bliptext.com/articles/stellar-parallax) value of 0.018 \". But limb darkening and measurement errors resulted in uncertainty about the accuracy of these measurements.\nThe 1950s and 1960s saw two developments that affected stellar [convection](https://bliptext.com/articles/convection) theory in red supergiants: the [Stratoscope](https://bliptext.com/articles/stratoscope) projects and the 1958 publication of Structure and Evolution of the Stars, principally the work of [Martin Schwarzschild](https://bliptext.com/articles/martin-schwarzschild) and his colleague at [Princeton University](https://bliptext.com/articles/princeton-university), Richard Härm.\nThis book disseminated ideas on how to apply computer technologies to create stellar models, while the Stratoscope projects, by taking balloon-borne telescopes above the Earth's [turbulence](https://bliptext.com/articles/wave-turbulence), produced some of the finest images of [solar granules](https://bliptext.com/articles/solar-granule) and [sunspots](https://bliptext.com/articles/sunspot) ever seen, thus confirming the existence of convection in the solar atmosphere.\n# [Sir John Herschel in 1846 | upload.wikimedia.org/wikipedia/commons/6/62/John///Herschel///1846///%28cropped%29.png]\n\n## Imaging breakthroughs\nAstronomers saw some major advances in astronomical imaging technology in the 1970s, beginning with [Antoine Labeyrie](https://bliptext.com/articles/antoine-mile-henry-labeyrie)'s invention of [speckle interferometry](https://bliptext.com/articles/speckle-interferometry), a process that significantly reduced the blurring effect caused by [astronomical seeing](https://bliptext.com/articles/astronomical-seeing).\nIt increased the [optical resolution](https://bliptext.com/articles/optical-resolution) of ground-based [telescopes](https://bliptext.com/articles/telescope), allowing for more precise measurements of Betelgeuse's photosphere.\nWith improvements in [infrared telescopy](https://bliptext.com/articles/infrared-telescopy) atop [Mount Wilson](https://bliptext.com/articles/mount-wilson-observatory), [Mount Locke](https://bliptext.com/articles/mcdonald-observatory), and [Mauna Kea](https://bliptext.com/articles/mauna-kea-observatories) in Hawaii, astrophysicists began peering into the complex circumstellar shells surrounding the supergiant, causing them to suspect the presence of huge gas bubbles resulting from convection.\nHowever, it was not until the late 1980s and early 1990s, when Betelgeuse became a regular target for [aperture masking interferometry](https://bliptext.com/articles/aperture-masking-interferometry), that breakthroughs occurred in visible-light and [infrared imaging](https://bliptext.com/articles/infrared-photography).\nPioneered by [J.E. Baldwin](https://bliptext.com/articles/john-e-baldwin) and colleagues of the [Cavendish Astrophysics Group](https://bliptext.com/articles/cavendish-astrophysics-group), the new technique employed a small mask with several holes in the telescope pupil plane, converting the [aperture](https://bliptext.com/articles/aperture) into an ad hoc interferometric array.\nThe technique contributed some of the most accurate measurements of Betelgeuse while revealing bright spots on the star's photosphere.\nThese were the first optical and infrared images of a stellar disk other than the [Sun](https://bliptext.com/articles/sun), taken first from ground-based interferometers and later from higher-resolution observations of the [COAST telescope](https://bliptext.com/articles/cambridge-optical-aperture-synthesis-telescope).\nThe \"bright patches\" or \"hotspots\" observed with these instruments appeared to corroborate a theory put forth by Schwarzschild decades earlier of massive [convection](https://bliptext.com/articles/convection-zone) cells dominating the stellar surface.\nIn 1995, the [Hubble Space Telescope](https://bliptext.com/articles/hubble-space-telescope)'s [Faint Object Camera](https://bliptext.com/articles/faint-object-camera) captured an [ultraviolet image](https://bliptext.com/articles/ultraviolet-astronomy) with a resolution superior to that obtained by ground-based interferometers—the first conventional-telescope image (or \"direct-image\" in NASA terminology) of the disk of another star.\nBecause [ultraviolet](https://bliptext.com/articles/ultraviolet) light is absorbed by the [Earth's atmosphere](https://bliptext.com/articles/atmosphere-of-earth), observations at these wavelengths are best performed by [space telescopes](https://bliptext.com/articles/space-telescope).\nThis image, like earlier pictures, contained a bright patch indicating a region in the southwestern quadrant 2,000 K hotter than the stellar surface.\nSubsequent ultraviolet spectra taken with the [Goddard High Resolution Spectrograph](https://bliptext.com/articles/goddard-high-resolution-spectrograph) suggested that the hot spot was one of Betelgeuse's poles of rotation.\nThis would give the rotational axis an inclination of about 20° to the direction of Earth, and a [position angle](https://bliptext.com/articles/position-angle) from [celestial North](https://bliptext.com/articles/celestial-pole) of about 55°.\n# [1998/9 UV HST images of Betelgeuse showing asymmetrical pulsations with corresponding spectral line profiles | upload.wikimedia.org/wikipedia/commons/4/43/Betelgeuse///pulsating///UV///%28HST%29.jpg]\n\n## 2000s studies\nIn a study published in December 2000, the star's diameter was measured with the [Infrared Spatial Interferometer](https://bliptext.com/articles/infrared-spatial-interferometer) (ISI) at mid-infrared wavelengths producing a limb-darkened estimate of 55.2 mas – a figure entirely consistent with Michelson's findings eighty years earlier.\nAt the time of its publication, the estimated parallax from the [Hipparcos](https://bliptext.com/articles/hipparcos) mission was 7.63 mas, yielding an estimated radius for Betelgeuse of 3.6 AU.\nHowever, an infrared interferometric study published in 2009 announced that the star had shrunk by 15% since 1993 at an increasing rate without a significant diminution in magnitude.\nSubsequent observations suggest that the apparent contraction may be due to shell activity in the star's extended atmosphere.\nIn addition to the star's diameter, questions have arisen about the complex dynamics of Betelgeuse's extended atmosphere.\nThe mass that makes up galaxies is recycled as [stars are formed and destroyed](https://bliptext.com/articles/life-cycle-of-stars), and red supergiants are major contributors, yet the process by which mass is lost remains a mystery.\nWith advances in interferometric methodologies, astronomers may be close to resolving this conundrum.\nImages released by the [European Southern Observatory](https://bliptext.com/articles/european-southern-observatory) in July 2009, taken by the ground-based [Very Large Telescope](https://bliptext.com/articles/very-large-telescope) Interferometer (VLTI), showed a vast plume of gas extending 30 AU from the star into the surrounding atmosphere.\nThis mass ejection was equal to the distance between the Sun and [Neptune](https://bliptext.com/articles/neptune) and is one of multiple events occurring in Betelgeuse's surrounding atmosphere.\nAstronomers have identified at least six shells surrounding Betelgeuse.\nSolving the mystery of mass loss in the late stages of a star's evolution may reveal those factors that precipitate the explosive deaths of these stellar giants.\n\n## 2019–2020 fading\nA pulsating [semiregular variable star](https://bliptext.com/articles/semiregular-variable-star), Betelgeuse is subject to multiple cycles of increasing and decreasing brightness due to changes in its size and temperature.\nThe astronomers who first noted the dimming of Betelgeuse, [Villanova University](https://bliptext.com/articles/villanova-university) astronomers Richard Wasatonic and [Edward Guinan](https://bliptext.com/articles/edward-guinan), and amateur Thomas Calderwood, theorize that a coincidence of a normal 5.9 year light-cycle minimum and a deeper-than-normal 425 day period are the driving factors.\nOther possible causes hypothesized by late 2019 were an eruption of gas or dust or fluctuations in the star's surface brightness.\nBy August 2020, long-term and extensive studies of Betelgeuse, primarily using [ultraviolet observations](https://bliptext.com/articles/ultraviolet-astronomy) by the [Hubble Space Telescope](https://bliptext.com/articles/hubble-space-telescope), had suggested that the unexpected dimming was probably caused by an immense amount of superhot material ejected into space.\nThe material cooled and formed a dust cloud that blocked the starlight coming from about a quarter of Betelgeuse's surface.\nHubble captured signs of dense, heated material moving through the star's atmosphere in September, October and November before several telescopes observed the more marked dimming in December and the first few months of 2020.\nBy January 2020, Betelgeuse had dimmed by a factor of approximately 2.5 from magnitude 0.5 to 1.5 and was reported still fainter in February in [The Astronomer's Telegram](https://bliptext.com/articles/the-astronomer-s-telegram) at a record minimum of +1.614, noting that the star is currently the \"least luminous and coolest\" in the 25 years of their studies and also calculating a decrease in radius.\n[Astronomy](https://bliptext.com/articles/astronomy-magazine) magazine described it as a \"bizarre dimming\",\nand popular speculation inferred that this might indicate an imminent [supernova](https://bliptext.com/articles/supernova).\nThis dropped Betelgeuse from one of the top 10 [brightest stars in the sky](https://bliptext.com/articles/list-of-brightest-stars) to outside the top 20, noticeably dimmer than its near neighbor [Aldebaran](https://bliptext.com/articles/aldebaran).\nMainstream media reports discussed speculation that Betelgeuse might be about to explode as a supernova,\nbut astronomers note that the supernova is expected to occur within approximately the next 100,000 years and is thus unlikely to be imminent.\nBy 17 February 2020, Betelgeuse's brightness had remained constant for about 10 days, and the star showed signs of rebrightening.\nOn 22 February 2020, Betelgeuse may have stopped dimming altogether, all but ending the dimming episode.\nOn 24 February 2020, no significant change in the infrared over the last 50 years was detected; this seemed unrelated to the recent visual fading and suggested that an impending core collapse may be unlikely.\nAlso on 24 February 2020, further studies suggested that occluding \"large-grain [circumstellar dust](https://bliptext.com/articles/circumstellar-dust)\" may be the most likely explanation for the dimming of the star.\nA study that uses [observations](https://bliptext.com/articles/observation) at [submillimetre](https://bliptext.com/articles/submillimetre-astronomy) wavelengths rules out significant contributions from dust absorption.\nInstead, large [starspots](https://bliptext.com/articles/starspot) appear to be the cause for the dimming.\nFollowup studies, reported on 31 March 2020 in The Astronomer's Telegram, found a rapid rise in the brightness of Betelgeuse.\nBetelgeuse is almost unobservable from the ground between May and August because it is too close to the Sun.\nBefore entering its 2020 [conjunction](https://bliptext.com/articles/conjunction-astronomy) with the Sun, Betelgeuse had reached a brightness of +0.4.\nObservations with the [STEREO-A](https://bliptext.com/articles/stereo) spacecraft made in June and July 2020 showed that the star had dimmed by 0.5 since the last ground-based observation in April.\nThis is surprising, because a maximum was expected for August/September 2020, and the next minimum should occur around April 2021.\nHowever Betelgeuse's brightness is known to vary irregularly, making predictions difficult.\nThe fading could indicate that another dimming event might occur much earlier than expected.\nOn 30 August 2020, astronomers reported the detection of a second dust cloud emitted from Betelgeuse, and associated with recent substantial dimming (a secondary minimum on 3 August) in luminosity of the star.\nIn June 2021, the dust was explained as possibly caused by a cool patch on its photosphere\nand in August a second independent group confirmed these results.\nThe dust is thought to have resulted from the cooling of gas ejected from the star.\nAn August 2022\nstudy using the [Hubble Space Telescope](https://bliptext.com/articles/hubble-space-telescope) confirmed previous research and suggested the dust could have been created by a surface mass ejection.\nIt conjectured as well that the dimming could have come from a short-term minimum coinciding with a long-term minimum producing a grand minimum, a 416-day cycle and 2010 day cycle respectively, a mechanism first suggested by astronomer [L. Goldberg](https://bliptext.com/articles/leo-goldberg).\nIn April 2023, astronomers reported the star reached a peak of 0.0 visual and 0.1 V-band magnitude.\n# [AAVSO V-band magnitude of Betelgeuse, between September 2016 and August 2023 | upload.wikimedia.org/wikipedia/commons/5/50/Betelgeuse///AAVSO///2019.jpg]\n# [Comparison of SPHERE images of Betelgeuse taken in January 2019 and December 2019, showing the changes in brightness and shape | upload.wikimedia.org/wikipedia/commons/0/0e/Eso2003c.jpg]\n\n# Observation\nAs a result of its distinctive orange-red color and position within Orion, Betelgeuse is easy to find with the naked eye.\nIt is one of three stars that make up the [Winter Triangle](https://bliptext.com/articles/winter-triangle) [asterism](https://bliptext.com/articles/asterism-astronomy), and it marks the center of the [Winter Hexagon](https://bliptext.com/articles/winter-hexagon).\nIt can be seen rising in the east at the beginning of January of each year, just after sunset.\nBetween mid-September and mid-March (best in mid-December), it is visible to virtually every inhabited region of the globe, except in [Antarctica](https://bliptext.com/articles/antarctica) at latitudes south of 82°.\nIn May (moderate northern latitudes) or June (southern latitudes), the red supergiant can be seen briefly on the western horizon after sunset, reappearing again a few months later on the eastern horizon before sunrise.\nIn the intermediate period (June–July, centered around mid June), it is invisible to the naked eye (visible only with a telescope in daylight), except around midday low in the north in Antarctic regions between 70° and 80° south latitude (during midday twilight in [polar night](https://bliptext.com/articles/polar-night), when the Sun is below the horizon).\nBetelgeuse is a variable star whose [visual magnitude](https://bliptext.com/articles/apparent-magnitude) ranges between 0.0 and +1.6.\nThere are periods during which it surpasses Rigel to become the sixth brightest star, and occasionally it will become even brighter than [Capella](https://bliptext.com/articles/capella).\nAt its faintest, Betelgeuse can fall behind [Deneb](https://bliptext.com/articles/deneb) and [Beta Crucis](https://bliptext.com/articles/beta-crucis), themselves both slightly variable, to be the twentieth-brightest star.\nBetelgeuse has a B–V [color index](https://bliptext.com/articles/color-index) of 1.85 – a figure which points to its pronounced \"redness\".\nThe photosphere has an extended [atmosphere](https://bliptext.com/articles/stellar-atmosphere), which displays strong lines of [emission](https://bliptext.com/articles/spectral-line) rather than [absorption](https://bliptext.com/articles/spectral-line), a phenomenon that occurs when a star is surrounded by a thick gaseous envelope (rather than ionized).\nThis extended gaseous atmosphere has been observed moving toward and away from Betelgeuse, depending on fluctuations in the photosphere.\nBetelgeuse is the brightest near-infrared source in the sky with a [J band](https://bliptext.com/articles/j-band-infrared) [magnitude](https://bliptext.com/articles/magnitude-astronomy) of −2.99; only about 13% of the star's [radiant energy](https://bliptext.com/articles/radiant-energy) is emitted as visible light.\nIf human eyes were sensitive to radiation at all wavelengths, Betelgeuse would appear as the brightest star in the night sky.\nCatalogues list up to nine faint visual companions to Betelgeuse.\nThey are at distances of about one to four arc-minutes and all are fainter than 10th magnitude.\n# [Image showing Betelgeuse (top left) and the dense nebulae of the Orion molecular cloud complex ( Rogelio Bernal Andreo ) | upload.wikimedia.org/wikipedia/commons/4/47/Orion///Head///to///Toe.jpg]\n# [Orion as seen on midday mid-June from Dome C (75 degrees South, Antarctica). Screenshot from Stellarium | upload.wikimedia.org/wikipedia/commons/0/08/Orion///from///Antarctica///in///polar///night.png]\n\n## Star system\nBetelgeuse is generally considered to be a single isolated star and a [runaway star](https://bliptext.com/articles/runaway-star), not currently associated with any cluster or star-forming region, although its birthplace is unclear.\nTwo spectroscopic companions to Betelgeuse have been proposed.\nAnalysis of [polarization](https://bliptext.com/articles/polarization-waves) data from 1968 through 1983 indicated a close companion with a periodic orbit of about 2.1 years, and by using [speckle interferometry](https://bliptext.com/articles/speckle-imaging), the team concluded that the closer of the two companions was located at 0.06 \" (≈9 AU) from the main star with a position angle of 273°, an orbit that would potentially place it within the star's [chromosphere](https://bliptext.com/articles/chromosphere). The more distant companion was at 0.51 \" (≈77 AU) with a position angle of 278°.\nFurther studies have found no evidence for these companions or have actively refuted their existence, but the possibility of a close companion contributing to the overall flux has never been fully ruled out.\nHigh-resolution interferometry of Betelgeuse and its vicinity, far beyond the technology of the 1980s and 1990s, has not detected any companions.\nA more recent study found that a not yet directly-observed, dust-modulating stellar-mass companion of would be the most likely solution for Betelgeuse's 2170-day secondary periodicity, fluctuating radial velocity, moderate radius and low variation in effective temperature.\nThe candidate companion would have a semi-major axis of 8.6 [AU](https://bliptext.com/articles/astronomical-unit).\n\n## Distance measurements\n[Parallax](https://bliptext.com/articles/parallax) is the apparent change of the position of an object, measured in seconds of arc, caused by the change of position of the observer of that object.\nAs the Earth orbits the Sun, every star is seen to shift by a fraction of an arc second, which measure, combined with the baseline provided by the Earth's orbit gives the distance to that star.\nSince the first successful [parallax](https://bliptext.com/articles/parallax) measurement by [Friedrich Bessel](https://bliptext.com/articles/friedrich-bessel) in 1838, astronomers have been puzzled by Betelgeuse's apparent distance.\nKnowledge of the star's distance improves the accuracy of other stellar parameters, such as [luminosity](https://bliptext.com/articles/stellar-luminosity) that, when combined with an angular diameter, can be used to calculate the physical radius and [effective temperature](https://bliptext.com/articles/effective-temperature); [luminosity](https://bliptext.com/articles/stellar-luminosity) and [isotopic abundances](https://bliptext.com/articles/natural-abundance) can also be used to estimate the [stellar age](https://bliptext.com/articles/stellar-evolution) and [mass](https://bliptext.com/articles/intermediate-mass-star).\nWhen the first interferometric studies were performed on the star's diameter in 1920, the assumed parallax was 0.018 \". This equated to a distance of 56 pc or roughly 180 ly, producing not only an inaccurate radius for the star but every other stellar characteristic. Since then, there has been ongoing work to measure the distance of Betelgeuse, with proposed distances as high as 400 pc or about 1,300 ly.\nBefore the publication of the [Hipparcos Catalogue](https://bliptext.com/articles/hipparcos-catalogue) (1997), there were two slightly conflicting parallax measurements for Betelgeuse.\nThe first, in 1991, gave a parallax of 9.8 mas, yielding a distance of roughly 102 pc or 330 ly.\nThe second was the [Hipparcos Input Catalogue](https://bliptext.com/articles/hipparcos) (1993) with a trigonometric parallax of 5 mas, a distance of 200 pc or 650 ly.\nGiven this uncertainty, researchers were adopting a wide range of distance estimates, leading to significant variances in the calculation of the star's attributes.\nThe results from the Hipparcos mission were released in 1997.\nThe measured parallax of Betelgeuse was 7.63 mas, which equated to a distance of roughly 131 pc or 427 ly, and had a smaller reported error than previous measurements.\nHowever, later evaluation of the Hipparcos parallax measurements for variable stars like Betelgeuse found that the uncertainty of these measurements had been underestimated.\nIn 2007, an improved figure of 6.55 was calculated, hence a much tighter [error factor](https://bliptext.com/articles/margin-of-error) yielding a distance of roughly 152 pc or 500 ly.\nIn 2008, measurements using the [Very Large Array](https://bliptext.com/articles/very-large-array) (VLA) produced a [radio](https://bliptext.com/articles/radio-astronomy) solution of 5.07 mas, equaling a distance of 197 pc or 643 ly.\nAs the researcher, Harper, points out: \"The revised Hipparcos parallax leads to a larger distance (152 pc) than the original; however, the [astrometric](https://bliptext.com/articles/astrometric) solution still requires a significant [cosmic noise](https://bliptext.com/articles/cosmic-noise) of 2.4 mas. Given these results it is clear that the Hipparcos data still contain systematic errors of unknown origin.\"\nAlthough the radio data also have systematic errors, the Harper solution combines the datasets in the hope of mitigating such errors.\nAn updated result from further observations with [ALMA](https://bliptext.com/articles/atacama-large-millimeter-array) and [e-Merlin](https://bliptext.com/articles/e-merlin) gives a parallax of 4.51 mas and a distance of 222 pc or 724 ly.\nIn 2020, new observational data from the space-based Solar Mass Ejection Imager aboard the [Coriolis satellite](https://bliptext.com/articles/coriolis-satellite) and three different modeling techniques produced a refined parallax of 5.95 mas, a radius of 764, and a distance of 168.1 pc or 548 ly, which, if accurate, would mean Betelgeuse is nearly 25% smaller and 25% closer to Earth than previously thought.\nAlthough the [European Space Agency](https://bliptext.com/articles/european-space-agency)'s current [Gaia mission](https://bliptext.com/articles/gaia-mission) was not expected to produce good results for stars brighter than the approximately V=6 saturation limit of the mission's instruments, actual operation has shown good performance on objects to about magnitude +3.\nForced observations of brighter stars mean that final results should be available for all bright stars and a parallax for Betelgeuse will be published an order of magnitude more accurate than currently available.\nThere is no data on Betelgeuse in [Gaia Data Release 2](https://bliptext.com/articles/gaia-data-release-2), which was released in 2018.\n# [NRAO's Very Large Array used to derive Betelgeuse's 2008 distance estimate | upload.wikimedia.org/wikipedia/commons/6/63/USA.NM.VeryLargeArray.02.jpg]\n\n## Variability\nBetelgeuse is classified as a [semiregular variable star](https://bliptext.com/articles/semiregular-variable-star), indicating that some periodicity is noticeable in the brightness changes, but amplitudes may vary, cycles may have different lengths, and there may be standstills or periods of irregularity.\nIt is placed in subgroup SRc; these are pulsating red supergiants with amplitudes around one magnitude and periods from tens to hundreds of days.\nBetelgeuse typically shows only small brightness changes near to magnitude +0.5, although at its extremes it can become as bright as magnitude 0.0 or as faint as magnitude +1.6.\nBetelgeuse is listed in the [General Catalogue of Variable Stars](https://bliptext.com/articles/general-catalogue-of-variable-stars) with a possible period of 2,335 days.\nMore detailed analyses have shown a main period near 400 days, a short period of 185 days, and a longer secondary period around 2,100 days.\nThe lowest reliably-recorded [V-band](https://bliptext.com/articles/ubv-photometric-system) magnitude of +1.614 was reported in February 2020.\nRadial pulsations of red supergiants are well-modelled and show that periods of a few hundred days are typically due to [fundamental](https://bliptext.com/articles/fundamental-mode) and first [overtone](https://bliptext.com/articles/overtone) pulsation.\n[Lines](https://bliptext.com/articles/absorption-line) in the [spectrum](https://bliptext.com/articles/stellar-spectrum) of Betelgeuse show [doppler shifts](https://bliptext.com/articles/doppler-shift) indicating [radial velocity](https://bliptext.com/articles/radial-velocity) changes corresponding, very roughly, to the brightness changes.\nThis demonstrates the nature of the pulsations in size, although corresponding temperature and spectral variations are not clearly seen.\nVariations in the diameter of Betelgeuse have also been measured directly.\n[First overtone](https://bliptext.com/articles/overtone) pulsations of 185 days have been observed, and the ratio of the fundamental to overtone periods gives valuable information about the internal structure of the star and its age.\nThe source of the long secondary periods is unknown, but they cannot be explained by [radial pulsations](https://bliptext.com/articles/radial-pulsations).\nInterferometric observations of Betelgeuse have shown hotspots that are thought to be created by massive convection cells, a significant fraction of the diameter of the star and each emitting 5–10% of the total light of the star.\nOne theory to explain long secondary periods is that they are caused by the evolution of such cells combined with the rotation of the star.\nOther theories include close binary interactions, [chromospheric](https://bliptext.com/articles/chromosphere) magnetic activity influencing mass loss, or non-radial pulsations such as [g-modes](https://bliptext.com/articles/g-mode-pulsation).\nIn addition to the discrete dominant periods, small-amplitude [stochastic](https://bliptext.com/articles/stochastic) variations are seen.\nIt is proposed that this is due to [granulation](https://bliptext.com/articles/granule-solar-physics), similar to the same effect on the sun but on a much larger scale.\n# [AAVSO V-band light curve of Betelgeuse (Alpha Orionis) from Dec 1988 to Aug 2002 | upload.wikimedia.org/wikipedia/commons/b/b7/Light///curve///of///Betelgeuse.png]\n# [Orion, with Betelgeuse at its usual magnitude (left) and during the unusually deep minimum in early 2020 (right) | upload.wikimedia.org/wikipedia/commons/a/ac/Betelgeuse.jpg]\n\n## Diameter\nOn 13 December 1920, Betelgeuse became the first star outside the Solar System to have the angular size of its photosphere measured.\nAlthough interferometry was still in its infancy, the experiment proved a success.\nThe researchers, using a uniform disk model, determined that Betelgeuse had a diameter of 0.047 \", although the stellar disk was likely 17% larger due to the [limb darkening](https://bliptext.com/articles/limb-darkening), resulting in an estimate for its angular diameter of about 0.055\".\nSince then, other studies have produced angular diameters that range from 0.042 to 0.069 \". Combining these data with historical distance estimates of 180 to 815 ly yields a projected radius of the stellar disk of anywhere from 1.2 to 8.9 AU. Using the Solar System for comparison, the orbit of [Mars](https://bliptext.com/articles/solar-system) is about 1.5 AU, [Ceres](https://bliptext.com/articles/solar-system) in the [asteroid belt](https://bliptext.com/articles/asteroid-belt) 2.7 AU, [Jupiter](https://bliptext.com/articles/solar-system) 5.5 AU—so, assuming Betelgeuse occupying the place of the Sun, its photosphere might extend beyond the Jovian orbit, not quite reaching [Saturn](https://bliptext.com/articles/solar-system) at 9.5 AU.\nThe precise diameter has been hard to define for several reasons:\nThe generally reported radii of large cool stars are [Rosseland radii](https://bliptext.com/articles/rosseland-optical-depth), defined as the radius of the photosphere at a specific optical depth of two-thirds.\nThis corresponds to the radius calculated from the effective temperature and bolometric luminosity.\nThe Rosseland radius differs from directly measured radii, with corrections for [limb darkening](https://bliptext.com/articles/limb-darkening) and the observation wavelength.\nFor example, a measured angular diameter of 55.6 mas would correspond to a Rosseland mean diameter of 56.2 mas, while further corrections for the existence of surrounding dust and gas shells would give a diameter of 41.9 mas.\nTo overcome these challenges, researchers have employed various solutions.\nAstronomical interferometry, first conceived by [Hippolyte Fizeau](https://bliptext.com/articles/hippolyte-fizeau) in 1868, was the seminal concept that has enabled major improvements in modern telescopy and led to the creation of the [Michelson interferometer](https://bliptext.com/articles/michelson-interferometer) in the 1880s, and the first successful measurement of Betelgeuse.\nJust as human [depth perception](https://bliptext.com/articles/depth-perception) increases when two eyes instead of one perceive an object, Fizeau proposed the observation of stars through two [apertures](https://bliptext.com/articles/apertures) instead of one to obtain [interferences](https://bliptext.com/articles/interference-wave-propagation) that would furnish information on the star's spatial intensity distribution.\nThe science evolved quickly and multiple-aperture interferometers are now used to capture [speckled images](https://bliptext.com/articles/speckle-imaging), which are synthesized using [Fourier analysis](https://bliptext.com/articles/fourier-analysis) to produce a portrait of high resolution.\nIt was this methodology that identified the hotspots on Betelgeuse in the 1990s.\nOther technological breakthroughs include [adaptive optics](https://bliptext.com/articles/adaptive-optics), [space observatories](https://bliptext.com/articles/space-observatory) like Hipparcos, [Hubble](https://bliptext.com/articles/hubble-space-telescope) and [Spitzer](https://bliptext.com/articles/spitzer-space-telescope), and the [Astronomical Multi-BEam Recombiner (AMBER)](https://bliptext.com/articles/amber-very-large-telescope), which combines the beams of three telescopes simultaneously, allowing researchers to achieve milliarcsecond [spatial resolution](https://bliptext.com/articles/spatial-resolution).\nObservations in different regions of the electromagnetic spectrum—the visible, near-infrared ([NIR](https://bliptext.com/articles/infrared)), mid-infrared (MIR), or radio—produce very different angular measurements.\nIn 1996, Betelgeuse was shown to have a uniform disk of 56.6 mas.\nIn 2000, a [Space Sciences Laboratory](https://bliptext.com/articles/space-sciences-laboratory) team measured a diameter of 54.7 mas, ignoring any possible contribution from hotspots, which are less noticeable in the mid-infrared.\nAlso included was a theoretical allowance for limb darkening, yielding a diameter of 55.2 mas.\nThe earlier estimate equates to a radius of roughly 5.6 AU or, assuming the 2008 Harper distance of 197 pc, a figure roughly the size of the Jovian orbit of 5.5 AU.\nIn 2004, a team of astronomers working in the near-infrared announced that the more accurate photospheric measurement was 43.33 mas.\nThe study also put forth an explanation as to why varying wavelengths from the visible to mid-infrared produce different diameters: the star is seen through a thick, warm extended atmosphere.\nAt short wavelengths (the visible spectrum) the atmosphere scatters light, thus slightly increasing the star's diameter.\nAt near-infrared wavelengths ([K](https://bliptext.com/articles/k-band-infrared) and [L bands](https://bliptext.com/articles/l-band-infrared)), the scattering is negligible, so the classical photosphere can be directly seen; in the mid-infrared the scattering increases once more, causing the thermal emission of the warm atmosphere to increase the apparent diameter.\nStudies with the [IOTA](https://bliptext.com/articles/infrared-optical-telescope-array) and VLTI published in 2009 brought strong support to the idea of dust shells and a molecular shell (MOLsphere) around Betelgeuse, and yielded diameters ranging from 42.57 to 44.28 mas with comparatively insignificant margins of error.\nIn 2011, a third estimate in the near-infrared corroborating the 2009 numbers, this time showing a limb-darkened disk diameter of 42.49 mas.\nThe near-infrared photospheric diameter of 43.33 mas at the Hipparcos distance of 152 pc equates to about 3.4 AU or.\nA 2014 paper derives an angular diameter of 42.28 mas (equivalent to a 41.01 mas uniform disc) using H and K band observations made with the VLTI AMBER instrument.\nIn 2009 it was announced that the radius of Betelgeuse had shrunk from 1993 to 2009 by 15%, with the 2008 angular measurement equal to 47 mas.\nUnlike most earlier papers, this study used measurements at one specific wavelength over 15 years.\nThe diminution in Betelgeuse's [apparent size](https://bliptext.com/articles/apparent-size) equates to a range of values between 56 mas seen in 1993 to 47 mas seen in 2008—a contraction of almost 0.9 AU in 15 years.\nThe observed contraction is generally believed to be a variation in just a portion of the extended atmosphere around Betelgeuse, and observations at other wavelengths have shown an increase in diameter over a similar period.\nThe latest models of Betelgeuse adopt a photospheric angular diameter of around 43 mas, with multiple shells out to 50–60 mas.\nAssuming a distance of 197 pc, this means a stellar diameter of 887 R_solar.\nOnce considered as having the largest angular diameter of any star in the sky after the [Sun](https://bliptext.com/articles/sun), Betelgeuse lost that distinction in 1997 when a group of astronomers measured [R Doradus](https://bliptext.com/articles/r-doradus) with a diameter of 57 mas, although [R Doradus](https://bliptext.com/articles/r-doradus), being much closer to Earth at about 200 ly, has a linear diameter roughly one-third that of Betelgeuse.\n# [Size comparison between Arcturus, Rigel, S Doradus, Antares, and Betelgeuse | upload.wikimedia.org/wikipedia/commons/0/03/Arcturus///to///Betelgeuse///comparison.jpg]\n# [Size comparison of Betelgeuse, Mu Cephei, KY Cygni, and V354 Cephei, according to Emily Levesque | upload.wikimedia.org/wikipedia/commons/5/50/Mukyv354.png]\n# [Radio image from 1998 showing the size of Betelgeuse's photosphere (circle) and the effect of convective forces on the star's atmosphere | upload.wikimedia.org/wikipedia/commons/7/75/Betelgeuse///radio///wavelengths.jpg]\n# [Infrared image of Betelgeuse, Meissa and Bellatrix with surrounding nebulae | upload.wikimedia.org/wikipedia/commons/d/d4/Orion%27s///Big///Head///Revealed///in///Infrared.jpg]\n\n## Occultations\nBetelgeuse is too far from the ecliptic to be occulted by the major planets, but those by some [asteroids](https://bliptext.com/articles/asteroid) (which are more wide-ranging and much more numerous) occur frequently.\nA partial occultation by the 19th magnitude asteroid occurred on 2 January 2012.\nIt was partial because the angular diameter of the star was larger than that of the asteroid; the brightness of Betelgeuse dropped by only about 0.01 magnitudes.\nThe 14th magnitude asteroid [319 Leona](https://bliptext.com/articles/319-leona) was predicted to occult on 12 December 2023, 01:12 UTC.\nTotality was at first uncertain, and the occulation was projected to only last approximately twelve seconds (visible on a narrow path on Earth's surface, the exact width and location of which was initially uncertain due to lack of precise knowledge of the size and path of the asteroid).\nProjections were later refined as more data were analyzed for a totality (\"ring of fire\") of approximately five seconds and a 60 km wide path stretching from Tajikistan, Armenia, Turkey, Greece, Italy, Spain, the Atlantic Ocean, Miami, Florida and the [Florida Keys](https://bliptext.com/articles/florida-keys) to parts of Mexico.\n(The serendiptous event would also afford detailed observations of 319 Leona itself.) Among other programmes 80 [amateur astronomers](https://bliptext.com/articles/citizen-science) in Europe alone have been coordinated by astrophysicist [Miguel Montargès](https://bliptext.com/articles/miguel-montarg-s), et al. of the [Paris Observatory](https://bliptext.com/articles/paris-observatory) for the event.\n# [Predicted path using SOLEX | upload.wikimedia.org/wikipedia/commons/6/6a/Leona///Betelgeuse.png]\n\n# Physical characteristics\nStar-sizes.jpg and several stars, including Betelgeuse: 1. Mercury < Mars < Venus < Earth\n2. Earth < Neptune < Uranus < Saturn < Jupiter\n3. Jupiter < Wolf 359 < Sun < Sirius\n4. Sirius < Pollux < Arcturus < Aldebaran\n5. Aldebaran < Rigel < Antares < Betelgeuse\n6. Betelgeuse < Mu Cephei < VV Cephei A < VY Canis Majoris\n]]\nBetelgeuse is a very large, luminous but cool star classified as an M1-2 Ia-ab [red supergiant](https://bliptext.com/articles/red-supergiant).\nThe letter \"M\" in this designation means that it is a red star belonging to the [M spectral class](https://bliptext.com/articles/class-m-star) and therefore has a relatively low photospheric temperature; the \"Ia-ab\" suffix [luminosity class](https://bliptext.com/articles/yerkes-spectral-classification-scheme) indicates that it is an intermediate-luminosity supergiant, with properties partway between a normal supergiant and a luminous supergiant.\nSince 1943, the spectrum of Betelgeuse has served as one of the stable anchor points by which other stars are classified.\nUncertainty in the star's surface temperature, diameter, and distance make it difficult to achieve a precise measurement of Betelgeuse's luminosity, but research from 2012 quotes a luminosity of around, assuming a distance of 200 pc.\nStudies since 2001 report effective temperatures ranging from 3,250 to 3,690 [K](https://bliptext.com/articles/kelvin).\nValues outside this range have previously been reported, and much of the variation is believed to be real, due to pulsations in the atmosphere.\nThe star is also a slow rotator and the most recent velocity recorded was 5.45 km/s —much slower than [Antares](https://bliptext.com/articles/antares) which has a rotational velocity of 20 km/s.\nThe rotation period depends on Betelgeuse's size and orientation to Earth, but it has been calculated to take 36 years to turn on its axis, inclined at an angle of around 60 ° to Earth.\nIn 2004, astronomers using computer simulations speculated that even if Betelgeuse is not rotating it might exhibit large-scale magnetic activity in its extended atmosphere, a factor where even moderately strong fields could have a meaningful influence over the star's dust, wind and mass-loss properties.\nA series of [spectropolarimetric](https://bliptext.com/articles/spectropolarimetry) observations obtained in 2010 with the [Bernard Lyot Telescope](https://bliptext.com/articles/bernard-lyot-telescope) at [Pic du Midi Observatory](https://bliptext.com/articles/pic-du-midi-observatory) revealed the presence of a weak magnetic field at the surface of Betelgeuse, suggesting that the giant convective motions of supergiant stars are able to trigger the onset of a small-scale [dynamo effect](https://bliptext.com/articles/dynamo-effect).\n\n## Mass\nBetelgeuse has no known orbital companions, so its mass cannot be calculated by that direct method.\nModern mass estimates from theoretical modelling have produced values of, with values of – from older studies.\nIt has been calculated that Betelgeuse began its life as a star of, based on a solar luminosity of 90,000–150,000.\nA novel method of determining the supergiant's mass was proposed in 2011, arguing for a current stellar mass of with an upper limit of 16.6 and lower of, based on observations of the star's intensity profile from narrow H-band interferometry and using a photospheric measurement of roughly 4.3 AU or.\nA probablystic age prior analysis give a current mass of and an initial mass of.\nBetelgeuse's mass can also be estimated based on its position on the [colormagnitudediagram (CMD)](https://bliptext.com/articles/hertzsprung-russell-diagram).\nBetelgeuse's color may have changed from yellow (or possibly orange; i.e. a yellow supergiant) to red in the last few thousand years, based on a 2022 review of historical records.\nThis color change combined with the CMD suggest a mass of and age of 14 Myr, and a distance from 125 to 150 parsecs (~400 to 500 light years).\n\n## Motion\nThe [kinematics](https://bliptext.com/articles/kinematics) of Betelgeuse are complex.\nThe age of Class M supergiants with an initial mass of is roughly 10 million years.\nStarting from its present position and motion, a projection back in time would place Betelgeuse around 290 parsecs farther from the [galactic plane](https://bliptext.com/articles/galactic-plane)—an implausible location, as there is no [star formation](https://bliptext.com/articles/star-formation) [region](https://bliptext.com/articles/molecular-cloud) there.\nMoreover, Betelgeuse's projected pathway does not appear to intersect with the [25 Ori](https://bliptext.com/articles/25-orionis) [subassociation](https://bliptext.com/articles/orion-ob1-association) or the far younger Orion Nebula Cluster (ONC, also known as Ori OB1d), particularly since [Very Long Baseline Array](https://bliptext.com/articles/very-long-baseline-array) astrometry yields a distance from Betelgeuse to the ONC of between 389 and 414 parsecs.\nConsequently, it is likely that Betelgeuse has not always had its current motion through space but has changed course at one time or another, possibly the result of a nearby [stellar explosion](https://bliptext.com/articles/supernova).\nAn observation by the [Herschel Space Observatory](https://bliptext.com/articles/herschel-space-observatory) in January 2013 revealed that the star's winds are crashing against the surrounding interstellar medium.\nThe most likely star-formation scenario for Betelgeuse is that it is a runaway star from the [Orion OB1 association](https://bliptext.com/articles/orion-ob1-association).\nOriginally a member of a high-mass multiple system within Ori OB1a, Betelgeuse was probably formed about 10–12 million years ago, but has evolved rapidly due to its high mass.\nH. Bouy and J. Alves suggested in 2015 that Betelgeuse may instead be a member of the newly discovered Taurion [OB association](https://bliptext.com/articles/ob-association).\n# [Map showing the Orion OB1 association, which contains the blue supergiants of Orion's Belt and the Orion Nebula. Betelgeuse is believed to be a runaway star that was ejected from the Orion OB1 association. | upload.wikimedia.org/wikipedia/commons/4/48/Orion///OB1///%26///25///Ori///Group.png]\n\n## Circumstellar dynamics\nIn the late phase of [stellar evolution](https://bliptext.com/articles/stellar-evolution), massive stars like Betelgeuse exhibit high rates of [mass loss](https://bliptext.com/articles/stellar-mass-loss), possibly as much as every 10,000 years, resulting in a complex [circumstellar environment](https://bliptext.com/articles/circumstellar-envelope) that is constantly in flux.\nIn a 2009 paper, stellar mass loss was cited as the \"key to understanding the evolution of the universe from the earliest cosmological times to the current epoch, and of planet formation and the formation of life itself\".\nHowever, the physical mechanism is not well understood.\nWhen [Martin Schwarzschild](https://bliptext.com/articles/martin-schwarzschild) first proposed his theory of huge convection cells, he argued it was the likely cause of mass loss in evolved supergiants like Betelgeuse.\nRecent work has corroborated this hypothesis, yet there are still uncertainties about the structure of their convection, the mechanism of their mass loss, the way dust forms in their extended atmosphere, and the conditions which precipitate their dramatic finale as a type II supernova.\nIn 2001, Graham Harper estimated a stellar wind at every 10,000 years, but research since 2009 has provided evidence of episodic mass loss making any total figure for Betelgeuse uncertain.\nCurrent observations suggest that a star like Betelgeuse may spend a portion of its lifetime as a [red supergiant](https://bliptext.com/articles/red-supergiant-star), but then cross back across the H–R diagram, pass once again through a brief [yellow supergiant](https://bliptext.com/articles/yellow-supergiant-star) phase and then explode as a [blue supergiant](https://bliptext.com/articles/blue-supergiant) or [Wolf–Rayet star](https://bliptext.com/articles/wolf-rayet-star).\nAstronomers may be close to solving this mystery.\nThey noticed a large plume of gas extending at least six times its stellar radius indicating that Betelgeuse is not shedding matter evenly in all directions.\nThe plume's presence implies that the spherical symmetry of the star's photosphere, often observed in the infrared, is not preserved in its close environment.\nAsymmetries on the stellar disk had been reported at different wavelengths.\nHowever, due to the refined capabilities of the [NACO](https://bliptext.com/articles/list-of-instruments-at-the-very-large-telescope) adaptive optics on the VLT, these asymmetries have come into focus.\nThe two mechanisms that could cause such asymmetrical mass loss, were large-scale convection cells or polar mass loss, possibly due to rotation.\nProbing deeper with ESO's AMBER, gas in the supergiant's extended atmosphere has been observed vigorously moving up and down, creating bubbles as large as the supergiant itself, leading his team to conclude that such stellar upheaval is behind the massive plume ejection observed by Kervella.\n# [Image from ESO's Very Large Telescope showing the stellar disk and an extended atmosphere with a previously unknown plume of surrounding gas | upload.wikimedia.org/wikipedia/commons/9/92/ESO-Betelgeuse.jpg]\n# [Artist's rendering from ESO showing Betelgeuse with a gigantic bubble boiling on its surface and a radiant plume of gas being ejected to six photospheric radii or roughly the orbit of Neptune | upload.wikimedia.org/wikipedia/commons/8/81/Betelgeuse///Plume///eso0927d.jpg]\n\n### Asymmetric shells\nIn addition to the photosphere, six other components of Betelgeuse's atmosphere have now been identified.\nThey are a molecular environment otherwise known as the MOLsphere, a gaseous envelope, a chromosphere, a dust environment and two outer shells (S1 and S2) composed of [carbon monoxide](https://bliptext.com/articles/carbon-monoxide) (CO).\nSome of these elements are known to be asymmetric while others overlap.\nAt about 0.45 stellar radii (~2–3 AU) above the photosphere, there may lie a molecular layer known as the MOLsphere or molecular environment.\nStudies show it to be composed of water vapor and carbon monoxide with an effective temperature of about 1,500 K. Water vapor had been originally detected in the supergiant's spectrum in the 1960s with the two Stratoscope projects but had been ignored for decades.\nThe MOLsphere may also contain [SiO](https://bliptext.com/articles/silicon-monoxide) and [Al2O3](https://bliptext.com/articles/aluminium-oxide)—molecules which could explain the formation of dust particles.\nAnother cooler region, the asymmetric gaseous envelope, extends for several radii (~10–40 AU) from the photosphere.\nIt is enriched in oxygen and especially in [nitrogen](https://bliptext.com/articles/nitrogen) relative to carbon.\nThese composition anomalies are likely caused by contamination by [CNO](https://bliptext.com/articles/cno-cycle)-processed material from the inside of Betelgeuse.\nRadio-telescope images taken in 1998 confirm that Betelgeuse has a highly complex atmosphere, with a temperature of 3,450 K, similar to that recorded on the star's surface but much lower than surrounding gas in the same region.\nThe VLA images also show this lower-temperature gas progressively cools as it extends outward.\nAlthough unexpected, it turns out to be the most abundant constituent of Betelgeuse's atmosphere.\n\"This alters our basic understanding of red-supergiant star atmospheres\", explained Jeremy Lim, the team's leader.\n\"Instead of the star's atmosphere expanding uniformly due to gas heated to high temperatures near its surface, it now appears that several giant convection cells propel gas from the star's surface into its atmosphere.\"\nThis is the same region in which Kervella's 2009 finding of a bright plume, possibly containing carbon and nitrogen and extending at least six photospheric radii in the southwest direction of the star, is believed to exist.\nThe [chromosphere](https://bliptext.com/articles/chromosphere) was directly imaged by the Faint Object Camera on board the Hubble Space Telescope in ultraviolet wavelengths.\nThe images also revealed a bright area in the southwest quadrant of the disk.\nThe average radius of the chromosphere in 1996 was about 2.2 times the optical disk (~10 AU) and was reported to have a temperature no higher than 5,500 K. However, in 2004 observations with the STIS, Hubble's high-precision spectrometer, pointed to the existence of warm chromospheric plasma at least one arcsecond away from the star.\nAt a distance of 197 pc, the size of the chromosphere could be up to 200 AU.\nThe observations have conclusively demonstrated that the warm chromospheric plasma spatially overlaps and co-exists with cool gas in Betelgeuse's gaseous envelope as well as with the dust in its circumstellar dust shells.\nThe first claim of a dust shell surrounding Betelgeuse was put forth in 1977 when it was noted that dust shells around mature stars often emit large amounts of radiation in excess of the photospheric contribution.\nUsing [heterodyne interferometry](https://bliptext.com/articles/interferometry), it was concluded that the red supergiant emits most of its excess radiation from positions beyond 12 stellar radii or roughly the distance of the [Kuiper belt](https://bliptext.com/articles/kuiper-belt) at 50 to 60 AU, which depends on the assumed stellar radius.\nSince then, there have been studies done of this dust envelope at varying wavelengths yielding decidedly different results.\nStudies from the 1990s have estimated the inner radius of the dust shell anywhere from 0.5 to 1 arcseconds, or 100 to 200 AU.\nThese studies point out that the dust environment surrounding Betelgeuse is not static.\nIn 1994, it was reported that Betelgeuse undergoes sporadic decades-long dust production, followed by inactivity.\nIn 1997, significant changes in the dust shell's morphology in one year were noted, suggesting that the shell is asymmetrically illuminated by a stellar radiation field strongly affected by the existence of photospheric hotspots.\nThe 1984 report of a giant asymmetric dust shell 1 pc (206,265 AU) has not been corroborated by recent studies, although another published the same year said that three dust shells were found extending four light-years from one side of the decaying star, suggesting that Betelgeuse sheds its outer layers as it moves.\nAlthough the exact size of the two outer [CO](https://bliptext.com/articles/carbon-monoxide) shells remains elusive, preliminary estimates suggest that one shell extends from about 1.5 to 4.0 [arcseconds](https://bliptext.com/articles/arcseconds) and the other expands as far as 7.0 [arcseconds](https://bliptext.com/articles/arcseconds).\nAssuming the Jovian orbit of 5.5 AU as the star radius, the inner shell would extend roughly 50 to 150 stellar radii (~300 to 800 AU) with the outer one as far as 250 stellar radii (~1,400 AU).\nThe Sun's [heliopause](https://bliptext.com/articles/heliopause-astronomy) is estimated at 100 AU, so the size of this outer shell would be almost fourteen times the size of the Solar System.\n# [Exterior view of ESO's Very Large Telescope (VLT) in Paranal, Chile | upload.wikimedia.org/wikipedia/commons/4/4b/ESO///Paranal///Platform.jpg]\n# [Interior view of one of the four 8.2-meter Unit Telescopes at ESO's VLT | upload.wikimedia.org/wikipedia/commons/9/97/Eso-paranal-16.jpg]\n# [This infrared image from the ESO's VLT shows complex shells of gas and dust around Betelgeuse – the tiny red circle in the middle is the size of the photosphere. | upload.wikimedia.org/wikipedia/commons/a/a0/Nebula///around///Betelgeuse.jpg]\n\n### Supersonic bow shock\nBetelgeuse is travelling through the interstellar medium at a speed of 30 km/second (i.e. ~6.3 AU/year) creating a [bow shock](https://bliptext.com/articles/bow-shocks-in-astrophysics).\nThe shock is not created by the star, but by its powerful [stellar wind](https://bliptext.com/articles/stellar-wind) as it ejects vast amounts of gas into the interstellar medium at a speed of 17 km/s, heating the material surrounding the star, thereby making it visible in infrared light.\nBecause Betelgeuse is so bright, it was only in 1997 that the bow shock was first imaged.\nThe [cometary](https://bliptext.com/articles/comet) structure is estimated to be at least one parsec wide, assuming a distance of 643 light-years.\n[Hydrodynamic](https://bliptext.com/articles/fluid-dynamics) simulations of the bow shock made in 2012 indicate that it is very young—less than 30,000 years old—suggesting two possibilities: that Betelgeuse moved into a region of the interstellar medium with different properties only recently or that Betelgeuse has undergone a significant transformation producing a changed stellar wind.\nA 2012 paper, proposed that this phenomenon was caused by Betelgeuse transitioning from a [blue supergiant](https://bliptext.com/articles/blue-supergiant) (BSG) to a red supergiant (RSG).\nThere is evidence that in the late evolutionary stage of a star like Betelgeuse, such stars \"may undergo rapid transitions from red to blue and vice versa on the Hertzsprung–Russell diagram, with accompanying rapid changes to their stellar winds and bow shocks.\"\nMoreover, if future research bears out this hypothesis, Betelgeuse may prove to have traveled close to 200,000 AU as a red supergiant scattering as much as 3 M_solar along its trajectory.\n\n# Life phases\nBetelgeuse is a red supergiant that has evolved from an [O-type main-sequence star](https://bliptext.com/articles/o-type-main-sequence-star).\nAfter core hydrogen exhaustion, Betelgeuse evolved into a blue supergiant before evolving into its current red supergiant form.\nIts core will eventually collapse, producing a [supernova](https://bliptext.com/articles/supernova) explosion and leaving behind a compact [remnant](https://bliptext.com/articles/supernova-remnant).\nThe details depend on the exact initial mass and other physical properties of that main sequence star.\n\n## Main sequence\nThe initial mass of Betelgeuse can only be estimated by testing different stellar evolutionary models to match its current observed properties.\nThe unknowns of both the models and the current properties mean that there is considerable uncertainty in Betelgeuse's initial appearance, but its mass is usually estimated to have been in the range of, with modern models finding values of.\nIts chemical makeup can be reasonably assumed to have been around 70% hydrogen, 28% helium, and 2.4% heavy elements, slightly more metal-rich than the Sun but otherwise similar.\nThe initial rotation rate is more uncertain, but models with slow to moderate initial rotation rates produce the best matches to Betelgeuse's current properties.\nThat main sequence version of Betelgeuse would have been a hot luminous star with a spectral type such as O9V.\nA star would take between 11.5 and 15 million years to reach the red supergiant stage, with more rapidly-rotating stars taking the longest.\nRapidly-rotating stars take 9.3 million years to reach the red supergiant stage, while stars with slow rotation take only 8.1 million years.\nThese are the best estimates of Betelgeuse's current age, as the time since its [zero age main sequence](https://bliptext.com/articles/main-sequence) stage is estimated to be 8.0–8.5 million years as a star with no rotation.\n# [Hertzsprung–Russell diagram identifying supergiants like Betelgeuse that have moved off the main sequence | upload.wikimedia.org/wikipedia/commons/9/96/Hertzsprung-Russell///Diagram///-///ESO.png]\n\n## After core hydrogen exhaustion\nBetelgeuse's time spent as a red supergiant can be estimated by comparing mass loss rates to the observed circumstellar material, as well as the abundances of heavy elements at the surface.\nEstimates range from 10,000 years to a maximum of 140,000 years.\nBetelgeuse appears to undergo short periods of heavy mass loss and is a runaway star moving rapidly through space, so comparisons of its current mass loss to the total lost mass are difficult.\nThe surface of Betelgeuse shows enhancement of nitrogen, relatively low levels of carbon, and a high proportion of [13C](https://bliptext.com/articles/carbon-13) relative to [12C](https://bliptext.com/articles/carbon-12), all indicative of a star that has experienced the [first dredge-up](https://bliptext.com/articles/dredge-up).\nHowever, the first dredge-up occurs soon after a star reaches the red supergiant phase and so this only means that Betelgeuse has been a red supergiant for at least a few thousand years.\nThe best prediction is that Betelgeuse has already spent around 40,000 years as a red supergiant, having left the main sequence perhaps one million years ago.\nThe current mass can be estimated from evolutionary models from the initial mass and the expected mass lost so far.\nFor Betelgeuse, the total mass lost is predicted to be no more than about, giving a current mass of , considerably higher than estimated by other means such as pulsational properties or limb-darkening models.\nAll stars more massive than about are expected to end their lives when their cores collapse, typically producing a supernova explosion.\nUp to about, a type II-P supernova is always produced from the red supergiant stage.\nMore massive stars can lose mass quickly enough that they evolve towards higher temperatures before their cores can collapse, particularly for rotating stars and models with especially high mass loss rates.\nThese stars can produce type II-L or type IIb supernovae from yellow or blue supergiants, or type I b/c supernovae from Wolf–Rayet stars.\nModels of rotating stars predict a peculiar type II supernova similar to [SN 1987A](https://bliptext.com/articles/sn-1987a) from a [blue supergiant](https://bliptext.com/articles/blue-supergiant) progenitor.\nOn the other hand, non-rotating models predict a type II-P supernova from a red [supergiant](https://bliptext.com/articles/supergiant) progenitor.\nThe time until Betelgeuse explodes depends on the predicted initial conditions and on the estimate of the time already spent as a red supergiant.\nThe total lifetime from the start of the red supergiant phase to core collapse varies from about 300,000 years for a rotating star, 550,000 years for a rotating star, and up to a million years for a non-rotating star.\nGiven the estimated time since Betelgeuse became a red supergiant, estimates of its remaining lifetime range from a \"best guess\" of under 100,000 years for a non-rotating model to far longer for rotating models or lower-mass stars.\nBetelgeuse's suspected birthplace in the [Orion OB1 association](https://bliptext.com/articles/orion-ob1-association) is the location of several previous supernovae.\nIt is believed that runaway stars may be caused by supernovae, and there is strong evidence that [OB stars](https://bliptext.com/articles/ob-star) [μ Columbae](https://bliptext.com/articles/mu-columbae), [AE Aurigae](https://bliptext.com/articles/ae-aurigae), and [53 Arietis](https://bliptext.com/articles/53-arietis) all originated from such explosions in Ori OB1 2.2, 2.7, and 4.9 million years ago.\nA typical type II-P [supernova](https://bliptext.com/articles/supernova) emits 2 J of [neutrinos](https://bliptext.com/articles/neutrino) and produces an explosion with a kinetic energy of 2 J. As seen from Earth, Betelgeuse as a type IIP [supernova](https://bliptext.com/articles/supernova) would have a peak apparent magnitude somewhere in the range −8 to −12.\nThis would be easily visible in daylight, with a possible brightness up to a significant fraction of the [full moon](https://bliptext.com/articles/full-moon), though likely not exceeding it.\nThis type of supernova would remain at roughly constant brightness for 2–3 months before rapidly dimming.\nThe visible light is produced mainly by the radioactive decay of [cobalt](https://bliptext.com/articles/cobalt), and sustains its brightness due to the increasing transparency of the cooling hydrogen ejected by the supernova.\n# [This is what Betelgeuse may have looked like up until about 1 million years ago, when it was a main-sequence star. | upload.wikimedia.org/wikipedia/commons/f/fc/O-type///star.png]\n# [Celestia depiction of Orion as it might appear from Earth when Betelgeuse explodes as a supernova, which could be brighter than the supernova that exploded in 1006 (SN 1006) | upload.wikimedia.org/wikipedia/commons/5/57/Betelgeuse///supernova.png]\n\n### Media reporting\nDue to misunderstandings caused by the 2009 publication of the star's 15% contraction, apparently of its outer atmosphere, Betelgeuse has frequently been the subject of scare stories and rumors suggesting that it will explode within a year, and leading to exaggerated claims about the consequences of such an event.\nThe timing and prevalence of these rumors have been linked to broader misconceptions of astronomy, particularly to doomsday predictions relating to the [Mayan calendrical apocalypse](https://bliptext.com/articles/2012-phenomenon).\nBetelgeuse is not likely to produce a [gamma-ray burst](https://bliptext.com/articles/gamma-ray-burst) and is not close enough for its [X-rays](https://bliptext.com/articles/x-ray), ultraviolet radiation, or ejected material to cause significant effects on [Earth](https://bliptext.com/articles/earth).\nFollowing the dimming of Betelgeuse in December 2019, reports appeared in the science and mainstream media that again included speculation that the star might be about to explode as a supernova – even in the face of scientific research that a supernova is not expected for perhaps 100,000 years.\nSome outlets reported the magnitude as faint as +1.3 as an unusual and interesting phenomenon, like Astronomy magazine, the [National Geographic](https://bliptext.com/articles/national-geographic), and the Smithsonian.\nSome mainstream media, like [The Washington Post](https://bliptext.com/articles/the-washington-post), [ABC News](https://bliptext.com/articles/abc-news-australia) in Australia, and [Popular Science](https://bliptext.com/articles/popular-science), reported that a supernova was possible but unlikely, whilst other outlets falsely portrayed a supernova as an imminent realistic possibility.\n[CNN](https://bliptext.com/articles/cnn), for example, chose the headline \"A giant red star is acting weird and scientists think it may be about to explode\", while the [New York Post](https://bliptext.com/articles/new-york-post) declared Betelgeuse as \"due for explosive supernova\".\n[Phil Plait](https://bliptext.com/articles/phil-plait), in his [Bad Astronomy](https://bliptext.com/articles/bad-astronomy) blog, noting that Betelgeuse's recent behaviour, \"[w]hile unusual . . . isn't unprecedented,\" argued that the star is not likely to explode \"for a long, long time.\"\n[Dennis Overbye](https://bliptext.com/articles/dennis-overbye) of [The New York Times](https://bliptext.com/articles/the-new-york-times) agreed that an explosion was not imminent but added that \"astronomers are having fun thinking about it.\"\nFollowing the eventual supernova, [a small dense remnant](https://bliptext.com/articles/compact-star) will be left behind, either a [neutron star](https://bliptext.com/articles/neutron-star) or [black hole](https://bliptext.com/articles/black-hole).\nBetelgeuse does not seem to have a core massive enough for a black hole, so the remnant will probably be a neutron star of approximately.\n\n# Ethnological attributes\n\n## Spelling and pronunciation\nBetelgeuse has also been spelled Betelgeux and, in [German](https://bliptext.com/articles/german-language), Beteigeuze (according to [Bode](https://bliptext.com/articles/johann-elert-bode)).\nBetelgeux and Betelgeuze were used until the early 20th century, when the spelling Betelgeuse became universal.\nConsensus on its pronunciation is weak and is as varied as its spellings:\nThe -urz pronunciations are attempts to render the French eu sound; they only work in r-dropping accents.\n\n## Etymology\nBetelgeuse is often mistranslated as \"armpit of the central one\".\nIn his 1899 work [Star-Names and Their Meanings](https://bliptext.com/articles/star-names), American amateur naturalist Richard Hinckley Allen stated the derivation was from the ابط الجوزاء , which he claimed degenerated into a number of forms, including Bed Elgueze, Beit Algueze, Bet El-gueze, and Beteigeuze, to the forms Betelgeuse, Betelguese, Betelgueze and Betelgeux.\nThe star was named Beldengeuze in the [Alfonsine Tables](https://bliptext.com/articles/alfonsine-tables), and Italian [Jesuit](https://bliptext.com/articles/jesuit) priest and astronomer [Giovanni Battista Riccioli](https://bliptext.com/articles/giovanni-battista-riccioli) had called it Bectelgeuze or Bedalgeuze.\nPaul Kunitzsch, Professor of Arabic Studies at the University of Munich, refuted Allen's derivation and instead proposed that the full name is a corruption of the Arabic يد الجوزاء , meaning \"the Hand of al-Jauzā '\" ; i.e., Orion.\nEuropean mistransliteration into [medieval Latin](https://bliptext.com/articles/medieval-latin) led to the first character y (**ﻴ**, with two dots underneath) being misread as a b (**ﺒ**, with only one dot underneath).\nDuring the [Renaissance](https://bliptext.com/articles/renaissance), the star's name was written as بيت الجوزاء **' (\"house of Orion\") or بط الجوزاء '**, incorrectly thought to mean \"armpit of Orion\" (a true translation of \"armpit\" would be ابط, transliterated as ).\nThis led to the modern rendering as Betelgeuse.\nOther writers have since accepted Kunitzsch's explanation.\nThe last part of the name, \"-elgeuse\", comes from the Arabic الجوزاء , a historical Arabic name of the constellation [Orion](https://bliptext.com/articles/orion-constellation), a feminine name in old [Arabian legend](https://bliptext.com/articles/arabian-legend), and of uncertain meaning.\nBecause جوز **', the [root](https://bliptext.com/articles/root-linguistics) of '**, means \"middle\", roughly means \"the Central One\".\nThe modern Arabic name for Orion is الجبار **' (\"the Giant\"), although the use of الجوزاء '** in the star's name has continued.\nThe 17th-century English translator [Edmund Chilmead](https://bliptext.com/articles/edmund-chilmead) gave it the name Ied Algeuze (\"Orion's Hand\"), from [Christmannus](https://bliptext.com/articles/jakob-christmann).\nOther Arabic names recorded include اليد اليمنى **' (\"the Right Hand\"), الذراع '** (\"the Arm\"), and المنكب **' (\"the Shoulder\"), all of al-Jauzā, Orion, as منكب الجوزاء '**.\n# [An illustration of Orion (horizontally reversed) in al-Sufi's Book of Fixed Stars. Betelgeuze is annotated as Yad al-Jauzā (\"Hand of Orion\"), one of the proposed etymological origins of its modern name, and also as Mankib al Jauzā' (\"Shoulder of Orion\"). | upload.wikimedia.org/wikipedia/commons/b/bd/Al-Sufi%27s///Orion%2C///1125///Baghdad///copy%2C///Doha///Museum///of///Islamic///Art///Ms///2.///1998.///SO.jpg]\n# [Dunhuang Star Chart, circa AD 700, showing 參宿四 Shēnxiùsì (Betelgeuse), the Fourth Star of the constellation of Three Stars | upload.wikimedia.org/wikipedia/commons/9/95/Dunhuang///Star///Atlas///-///Orion.jpg]\n\n## Other names\nOther names for Betelgeuse included the Persian Bašn \"the Arm\", and [Coptic](https://bliptext.com/articles/coptic-language) Klaria \"an Armlet\".\nBahu was its [Sanskrit](https://bliptext.com/articles/sanskrit) name, as part of a Hindu understanding of the constellation as a running antelope or stag.\nIn traditional [Chinese astronomy](https://bliptext.com/articles/chinese-astronomy), the [name](https://bliptext.com/articles/chinese-star-names) for Betelgeuse is 参宿四 (Shēnxiùsì, the Fourth Star of the constellation of [Three Stars](https://bliptext.com/articles/three-stars-chinese-constellation)) as the [Chinese constellation](https://bliptext.com/articles/orion-in-chinese-astronomy) 参宿 originally referred to the three stars in [Orion's Belt](https://bliptext.com/articles/orion-s-belt).\nThis constellation was ultimately expanded to ten stars, but the earlier name stuck.\nIn Japan, the [Taira, or Heike, clan](https://bliptext.com/articles/heike-clan) adopted Betelgeuse and its red color as its symbol, calling the star Heike-boshi, (平家星), while the [Minamoto, or Genji, clan](https://bliptext.com/articles/minamoto-clan) chose Rigel and its white color.\nThe two powerful families fought a [legendary war](https://bliptext.com/articles/genpei-war) in Japanese history, the stars seen as facing each other off and only kept apart by the Belt.\nIn Tahitian lore, Betelgeuse was one of the pillars propping up the sky, known as Anâ-varu, the pillar to sit by.\nIt was also called Ta'urua-nui-o-Mere \"Great festivity in parental yearnings\".\nA Hawaiian term for it was Kaulua-koko (\"brilliant red star\").\nThe [Lacandon people](https://bliptext.com/articles/lacandon-people) of Central America knew it as chäk tulix (\"red butterfly\").\nAstronomy writer [Robert Burnham Jr.](https://bliptext.com/articles/robert-burnham-jr) proposed the term padparadaschah, which denotes a rare orange sapphire in India, for the star.\n\n## Mythology\nWith the [history of astronomy](https://bliptext.com/articles/history-of-astronomy) intimately associated with mythology and astrology before the [scientific revolution](https://bliptext.com/articles/scientific-revolution), the red star, like the planet Mars that derives its name from a [Roman war god](https://bliptext.com/articles/mars-mythology), has been closely associated with the martial [archetype](https://bliptext.com/articles/archetype) of conquest for millennia, and by extension, the motif of death and rebirth.\nOther cultures have produced different myths.\nStephen R. Wilk has proposed the constellation of Orion could have represented the Greek mythological figure [Pelops](https://bliptext.com/articles/pelops), who had an artificial shoulder of ivory made for him, with Betelgeuse as the shoulder, its color reminiscent of the reddish yellow sheen of ivory.\n[Aboriginal](https://bliptext.com/articles/australian-aborigines) people from the [Great Victoria Desert](https://bliptext.com/articles/great-victoria-desert) of South Australia incorporated Betelgeuse into their oral traditions as the club of Nyeeruna (Orion), which fills with fire-magic and dissipates before returning.\nThis has been interpreted as showing that early Aboriginal observers were aware of the brightness variations of Betelgeuse.\nThe [Wardaman people](https://bliptext.com/articles/wardaman-people) of northern Australia knew the star as Ya-jungin (\"Owl Eyes Flicking\"), its variable light signifying its intermittent watching of ceremonies led by the Red Kangaroo Leader Rigel.\nIn South African mythology, Betelgeuse was perceived as a lion casting a predatory gaze toward the three zebras represented by Orion's Belt.\nIn the Americas, Betelgeuse signifies a severed limb of a man-figure (Orion)—the [Taulipang](https://bliptext.com/articles/pemon-people) of Brazil know the constellation as Zililkawai, a hero whose leg was cut off by his wife, with the variable light of Betelgeuse linked to the severing of the limb.\nSimilarly, the [Lakota people](https://bliptext.com/articles/lakota-people) of North America see it as a chief whose arm has been severed.\nA Sanskrit name for Betelgeuse is ārdrā (\"the moist one\"), eponymous of the [Ardra](https://bliptext.com/articles/ardra-nakshatra) [lunar mansion](https://bliptext.com/articles/nakshatra) in [Hindu astrology](https://bliptext.com/articles/hindu-astrology).\nThe [Rigvedic God](https://bliptext.com/articles/rigvedic-deities) of storms [Rudra](https://bliptext.com/articles/rudra) presided over the star; this association was linked by 19th-century star enthusiast [Richard Hinckley Allen](https://bliptext.com/articles/star-names-their-lore-and-meaning) to Orion's stormy nature.\nThe constellations in Macedonian folklore represented agricultural items and animals, reflecting their way of life.\nTo them, Betelgeuse was Orach (\"the ploughman\"), alongside the rest of Orion, which depicted a plough with oxen.\nThe rising of Betelgeuse at around 3 a.m. in late summer and autumn signified the time for village men to go to the fields and plough.\nTo the [Inuit](https://bliptext.com/articles/inuit-astronomy), the appearance of Betelgeuse and [Bellatrix](https://bliptext.com/articles/bellatrix) high in the southern sky after sunset marked the beginning of spring and lengthening days in late February and early March.\nThe two stars were known as Akuttujuuk (\"those [two] placed far apart\"), referring to the distance between them, mainly to people from North Baffin Island and Melville Peninsula.\nThe opposed locations of Orion and [Scorpius](https://bliptext.com/articles/scorpius), with their corresponding bright red variable stars Betelgeuse and [Antares](https://bliptext.com/articles/antares), were noted by ancient cultures around the world.\nThe setting of Orion and rising of Scorpius signify the death of Orion by the scorpion.\nIn China they signify brothers and rivals Shen and Shang.\nThe [Batak](https://bliptext.com/articles/batak-indonesia) of Sumatra marked their New Year with the first [new moon](https://bliptext.com/articles/new-moon) after the sinking of Orion's Belt below the horizon, at which point Betelgeuse remained \"like the tail of a rooster\".\nThe positions of Betelgeuse and Antares at opposite ends of the celestial sky were considered significant, and their constellations were seen as a pair of scorpions.\nScorpion days marked as nights that both constellations could be seen.\n\n## In popular culture\nAs one of the brightest and best-known stars, Betelgeuse has featured in many works of fiction.\nThe star's unusual name inspired the title of the 1988 film [Beetlejuice](https://bliptext.com/articles/beetlejuice), referring to its titular antagonist, and script writer [Michael McDowell](https://bliptext.com/articles/michael-mcdowell-author) was impressed by how many people made the connection.\nIn the popular science fiction series [The Hitchhiker's Guide to the Galaxy](https://bliptext.com/articles/the-hitchhiker-s-guide-to-the-galaxy) by [Douglas Adams](https://bliptext.com/articles/douglas-adams), [Ford Prefect](https://bliptext.com/articles/ford-prefect-character) was from \"a small planet somewhere in the vicinity of Betelgeuse.\"\nTwo American navy ships were named after the star, both of them World War II vessels, the USS Betelgeuse (AKA-11) launched in 1939 and USS Betelgeuse (AK-260) launched in 1944.\nIn 1979, the French supertanker [Betelgeuse](https://bliptext.com/articles/whiddy-island-disaster) was moored off [Whiddy Island](https://bliptext.com/articles/whiddy-island), discharging oil when it exploded, killing 50 people in one of the worst disasters in Ireland's history.\nThe [Dave Matthews Band](https://bliptext.com/articles/dave-matthews-band) song \"[Black and Blue Bird](https://bliptext.com/articles/black-and-blue-bird-song)\" references the star.\nThe [Blur](https://bliptext.com/articles/blur-band) song \"Far Out\" from their 1994 album [Parklife](https://bliptext.com/articles/parklife) mentions Betelgeuse in its lyrics.\nThe [Philip Larkin](https://bliptext.com/articles/philip-larkin) poem \"The North Ship\", found in [the collection of the same name](https://bliptext.com/articles/the-north-ship), references the star in the section \"Above 80° N\", which reads: \" 'A woman has ten claws,' / Sang the drunken boatswain; / Farther than Betelgeuse, / More brilliant than Orion / Or the planets Venus and Mars, / The star flames on the ocean; / 'A woman has ten claws,' / Sang the drunken boatswain.\"\n[Humbert Wolfe](https://bliptext.com/articles/humbert-wolfe) wrote a poem about Betelgeuse, which was set to music by [Gustav Holst](https://bliptext.com/articles/gustav-holst).\n\n# Table of angular diameter estimates\nThis table provides a non-exhaustive list of angular measurements conducted since 1920.\nAlso included is a column providing a current range of radii for each study based on Betelgeuse's most recent distance estimate (Harper et al.) of 197 pc.","revisionCount":1},"hasMore":false,"nextCursor":null}

History