Markarian 231 (UGC 8058) is a Type-1 Seyfert galaxy that was discovered in 1969 as part of a search of galaxies with strong ultraviolet radiation. It contains the nearest known quasar. Markarian 231 is located about 581 million light years away from Earth, in the constellation of Ursa Major.

Characteristics

Markarian 231 is undergoing an energetic starburst. A nuclear ring at the center has an active rate of star formation of greater than 100 solar masses per year. It is one of the most ultraluminous infrared galaxies, with power derived from an accreting black hole in the center forming the closest known quasar. X-ray data shows the energy released from the black hole produces ultra-fast outflows with a velocity of -20,000 km s-1. The galaxy contains a curved radio jet interacting with the interstellar medium. Its position angle switches to -172○ when reaching a projected distance of 25 pc. The Very Long Baseline Array found a triple radio source in Markarian 231. A 2015 study suggested the central black hole of 150 million solar masses has a black hole companion of 4 million solar masses, and that they orbit each other every 1.2 years. That model has been shown to be unfeasible. Submillimetre astronomy has found evidence of molecular oxygen (O2), the first time molecular oxygen has been detected outside of the Milky Way galaxy. The Herschel Space Observatory showed water vapor in the galaxy's emission.