19521 Chaos

Lore & Background

Chaos was discovered in 1998 by the Deep Ecliptic Survey with Kitt Peak's 4 m (13 ft) telescope. On 28 March 2002, it was 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, though Michael Moorcock's Symbol of Chaos has occasionally been used. Occultations suggest it is a compact or contact binary equivalent to a sphere 400 to 500 km (250 to 310 mi) 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 (370 mi) in diameter. Another occultation was recorded on 14 January 2022, but full results on size, shape, geometric albedo, and spin-axis orientation have not been released. A further occultation occurred on 28 September 2023, with a shadow crossing most of North America, observed by over 30 observers; preliminary analysis suggests that Chaos is a binary (possibly a contact binary). Chaos has an orbital period of approximately 309 years. Its orbit is longer, but less eccentric than the orbit of Pluto. Its 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 AU from Earth. Its brightest magnitude will be 20.8.

Reader's Guide

19521 Chaos is significant as a cubewano, a class of Kuiper belt objects not in resonance with any planet, and as a target of multiple occultation campaigns that have revealed its likely binary or contact binary nature. The 2020 occultation, observed by three detectors, constrained its diameter to under 600 km, while the 2023 occultation, observed by over 30 observers across most of North America, provided preliminary evidence for binarity. These observations contribute to understanding the physical properties and formation history of trans-Neptunian objects. Its naming after the primeval state in Greek mythology reflects a tradition of mythological names for such bodies. The lack of a standard symbol for Chaos in astronomy or astrology highlights the decline of planetary symbols in modern practice. Its orbit, with a 309-year period and a perihelion in December 2033, places it in the outer solar system, never crossing Neptune's orbit, with a minimum orbital intersection distance of 12.5 AU from Neptune. The ongoing analysis of occultation data, including the 2022 event whose results remain unreleased, underscores the dynamic nature of research on this object.

Did You Know?

• Preliminary analysis of the 28 September 2023 occultation suggests Chaos is a binary (possibly a contact binary).
• Chaos will come to perihelion around December 2033 at 40 AU from Earth.