2060 Chiron

2060 Chiron

Discovery A
Discoverer	Charles T. Kowal
Discovery date	October 18, 1977
Alternate designations	1977 UB B
Category	Centaur, Comet
Orbital elements C
Epoch May 10, 2005 (JD 2453500.5)
Eccentricity (e)	0.382
Semi-major axis (a)	2045.041 Gm (13.670 AU)
Perihelion (q)	1263.962 Gm (8.449 AU)
Aphelion (Q)	2826.120 Gm (18.891 AU)
Orbital period (P)	18461.347 d (50.54 a)
Mean orbital speed	7.75 km/s
Inclination (i)	6.935°
Longitude of the ascending node (Ω))	209.231°
Argument of perihelion (ω)	339.606°
Mean anomaly (M)	65.733°
Physical characteristics
Dimensions	132-142 km 1
Mass	2.4-3.0×1018 kg
Density	2.0? g/cm³
Surface gravity	0.037-0.040 m/s²
Escape velocity	0.070-0.075 km/s
Rotation period	0.2466 d (5.918 h) 2
Spectral class	?
Absolute magnitude	6.5
Albedo	0.10?
Mean surface temperature	~75 K

2060 Chiron (IPA: [kaɪ ron]) is an object in the outer solar system with an orbit between those of Saturn and Uranus and a radius of 71±5 km [1]. Although it was initially classified as an asteroid, later dispute arose as to whether it was an asteroid or actually a comet. It was discovered in 1977 by Charles T. Kowal and named after Chiron of Greek legend. Chiron should not be confused with the moon of Pluto named Charon, discovered in 1978.

In 1988 it was found that Chiron was undergoing an outburst in brightness (by about one magnitude), which is behaviour typical of comets but not asteroids. Further observations in 1989 showed that Chiron had developed a cometary coma.

At the time of its discovery, Chiron was close to aphelion, whereas the observations showing a coma were done closer to perihelion, perhaps explaining why no cometary behavior had been seen earlier.

Chiron is officially both a comet and an asteroid, more proof of the very fuzzy dividing line. As a comet, its name is 95P/Chiron. There are two other asteroids that are also listed as comets: 4015 Wilson-Harrington and 7968 Elst-Pizarro.

Chiron is now classified as a centaur, the first of a class of objects orbiting between the outer planets. Centaurs are not in stable orbits and will eventually be removed by the giant planets. Chiron is probably a refugee from the Kuiper belt.

Other centaurs such as 5145 Pholus are being observed for possible cometary behavior, but none has been seen so far.

Its discovery was publicized enough in the popular press that a school in astrology emerged assigning it a great importance.

References

Luu JX, Jewitt DC, Trujillo C (2000). Water Ice in 2060 Chiron and Its Implications for Centaurs and Kuiper Belt Objects. Astrophysical Journal 531 (2): L151-L154. PMID 10688775

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