2060 Chiron
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| Discovery A | |
|---|---|
| Discoverer | Charles T. Kowal |
| Discovery date | October 18, 1977 |
| Alternate designations B |
1977 UB, 95P/Chiron |
| Category | Centaur, Comet |
| Orbital elements C | |
|
|
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| Eccentricity (e) | 0.382 |
| Semi-major axis (a) | 2.045 Gm (13.670 AU) |
| Perihelion (q) | 1.263 Gm (8.449 AU) |
| Aphelion (Q) | 2.826 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 D | |
| 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 (geometric) | 0.10? |
| Mean surface temperature |
~75 K |
2060 Chiron (kye'-rən, IPA: /ˈkaɪrən/) is a planetoid in the outer solar system. Discovered in 1977 by Charles T. Kowal, it was the first known member of a new class of objects now known as Centaurs, with an orbit between those of Saturn and Uranus.
Although it was initially classified as an asteroid, later dispute arose as to whether it was an asteroid or actually a comet. Today it is classified as both, and accordingly it is also known by the cometary designation 95P/Chiron.
Chiron is named after the centaur Chiron in Greek mythology. It should not be confused with the largest moon of Pluto named Charon, discovered in 1978.
Contents |
[edit] Orbit
Chiron's orbit was found to be highly eccentric, with perihelion just inside the orbit of Saturn and aphelion just inside the orbit of Uranus (thus, it crosses Saturn's orbit, but not that of Uranus). It attracted considerable interest because it was the first object discovered in such an orbit, well outside the asteroid belt. 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 gravitational perturbation by the giant planets, moving to different orbits or leaving the solar system altogether.
It has been calculated that in 1664 BC Chiron approached Saturn to within approximately 16 million kilometres; only 3 million km further away than Saturn's largest outer moon Phoebe, and within the orbital radii of many of Saturn's newly discovered minor satellites. Chiron is probably a refugee from the Kuiper belt.
[edit] Physical characteristics
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 designated as both a comet and an asteroid, an indication of the sometimes fuzzy dividing line between the two classes of object. The term proto-comet has also been used. At approximately 180km across, it is unusually large for a comet nucleus.
Since the discovery of Chiron, quite a few other Centaurs have been discovered, and nearly all are currently classified as asteroids but are being observed for possible cometary behavior. As of March 2006, only one has been observed to have a cometary coma: 60558 Echeclus, which now also has the cometary designation 174P/Echeclus.
There are also three other non-Centaur asteroids that are also classified as comets: 4015 Wilson-Harrington, 7968 Elst-Pizarro, and 118401 LINEAR.
[edit] 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. Preprint on arXiv.
- Fernandez Y.R., Jewitt DC, Sheppard S (2002). "Thermal Properties of Centaurs Asbolus and Chiron". Astrophysical Journal 123: 1050–1055. Preprint on arXiv.
- Patrick Moore Guinness book of Astronomy ISBN 0-85112-375-9
[edit] External links
- Orbit visualisation. (Requires Java)
| Minor planets | ||
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| Previous minor planet | 2060 Chiron | Next minor planet |
| Comets | ||
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| Previous periodic comet | 95P/Chiron | Next periodic comet |
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| Vulcanoids | Near-Earth asteroids | Main belt | Jupiter Trojans | Centaurs | Damocloids | Comets | Trans-Neptunians (Kuiper belt · Scattered disc · Oort cloud) |
| For other objects and regions, see: asteroid groups and families, binary asteroids, asteroid moons and the Solar system For a complete listing, see: List of asteroids. See also Pronunciation of asteroid names and Meanings of asteroid names. |
