19521 Chaos

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.

19521 Chaos

19521 Chaos as imaged by the Hubble Space Telescope in September 2001
Discovery
Discovered by	Deep Ecliptic Survey
Discovery date	19 November 1998
Designations
MPC designation	(19521) Chaos
Pronunciation	/ˈkeɪ.ɒs/
Named after	Chaos
Alternative designations	1998 WH24
Minor planet category	TNO (cubewano)[1][2]
Adjectives	Chaotian /keɪˈoʊʃən/[3]
Symbol	(astrological)
Orbital characteristics[4]
Epoch 13 January 2016 (JD 2457400.5)
Uncertainty parameter 3
Observation arc	5902 days (16.16 yr)
Earliest precovery date	17 October 1991
Aphelion	50.636 AU (7.5750 Tm)
Perihelion	40.957 AU (6.1271 Tm)
Semi-major axis	45.796 AU (6.8510 Tm)
Eccentricity	0.10567
Orbital period (sidereal)	309.92 yr (113199 d)
Average orbital speed	4.3931 km/s
Mean anomaly	337.2998°
Mean motion	0° 0m 11.449s / day
Inclination	12.0502°
Longitude of ascending node	50.0239°
Time of perihelion	≈ 23 December 2033[5] ±10 days
Argument of perihelion	58.4097°
Known satellites	compact or contact binary
Jupiter MOID	35.8 AU (5.36 Tm)
Neptune MOID	12.5 AU (1.87 Tm)[6]
TJupiter	5.884
Physical characteristics
Dimensions	415+83 −30 km equivalent[7] 600+140 −130 km [8] ~665 [9]
Geometric albedo	ca. 0.1
Spectral type	B–V=0.95±0.03 [9] V–R=0.63±0.03 [9] V–I=1.25±0.04 [9]
Absolute magnitude (H)	4.8 [4] 5.0 [9]

Occultations suggest it is a compact or contact binary equivalent to a sphere 400 to 500 km in diameter.^[7] 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.^[10] Another occultation was recorded on 14 January 2022; full results on size, shape, geometric albedo, and the spin-axis orientation have not been released.^{[11][needs update]} A further occultation occurred on 28 September 2023, with a shadow crossing most of North America. This occultation was observed by over 30 observers;^[12] preliminary analysis suggests that Chaos is a binary (possibly a contact binary).^[13]

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 occasionally been used.^[14]

Orbit

Chaos has an orbital period of approximately 309 years. Its orbit is longer, but less eccentric than the orbit of Pluto. 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 (1.87 billion km).^[6]

Chaos will come to perihelion at around December 2033,^[5] coming as close as 40 AUs from Earth. Its brightest magnitude will be 20.8.