19521 Chaos is a cubewano, a Kuiper-belt object not in resonance with any planet. Chaos was discovered in 1998 by the Deep Ecliptic Survey with Kitt Peak's 4 m telescope. Occultations suggest it is a compact or contact binary equivalent to a sphere 400 to 500 km in diameter. On 20 November 2020, Chaos occulted a magnitude 16.8 star. Three observers detected the occultation, finding that the object is likely smaller than 600 km in diameter. Another occultation was recorded on 14 January 2022; full results on size, shape, geometric albedo, and the spin-axis orientation have not been released. A further occultation occurred on 28 September 2023, with a shadow crossing most of North America. This occultation was observed by over 30 observers; preliminary analysis suggests that Chaos is a binary (possibly a contact binary).

Name

It is named after the primeval state of existence in Greek mythology, from which the first gods appeared. Planetary symbols are no longer much used in astronomy, so Chaos never received a symbol in the astronomical literature. There is no standard symbol for Chaos used by astrologers either. Michael Moorcock's Symbol of Chaos has been used.

Orbit

19521 Chaos has an orbital period of approximately 309 years. Its orbit is longer, but less eccentric than the orbit of Pluto. 19521 Chaos's orbit is inclined approximately 12° to the ecliptic. Its orbit never crosses the orbit of Neptune. Currently, the closest approach possible to Neptune (MOID) is 12.5 AU. Chaos will come to perihelion at around December 2033, coming as close as 40 AUs from Earth. Its brightest magnitude will be 20.8.