5145 Pholus
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Discovery
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|---|---|
| Discovered by | Spacewatch (David L. Rabinowitz) |
| Discovery date | January 9, 1992 |
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Designations
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| Alternate name | 1992 AD |
| Minor planet category |
Centaur, Asteroid |
| Epoch November 30, 2008 (JD 2454800.5) | |
| Aphelion | 4784.1 Gm (31.98 AU) |
| Perihelion | 1305.9 Gm (8.730 AU) |
| Semi-major axis | 3045.2 Gm (20.356 AU) |
| Eccentricity | 0.5711 |
| Orbital period | 33547.41 d (91.85 yr) |
| Average orbital speed | 6.01 km/s |
| Mean anomaly | 67.49° |
| Inclination | 24.65° |
| Longitude of ascending node | 119.44° |
| Argument of perihelion | 354.92° |
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Physical characteristics
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| Dimensions | 185±16 km [1] |
| Mass | ~6.6×1018 kg |
| Mean density | 2.0? g/cm³ (assumed) |
| Equatorial surface gravity | ~0.052 m/s² |
| Escape velocity | ~0.098 km/s |
| Rotation period | 9.98 hours[1] |
| Albedo | 0.046±0.02 |
| Temperature | ~62 K |
| Spectral type | (red) B-V=1.19; V-R=0.78 [2] |
| Absolute magnitude (H) | 7.0[1] |
5145 Pholus (pronounced /ˈfoʊləs/ foe'-ləs, from Greek: Φόλος) is a centaur (minor planetoid) of the solar system running in an eccentric orbit, with a perihelion less than Saturn's and aphelion greater than Neptune's. Close approches of the object are rare: it has not come within one astronomical unit of a planet since 764 BC, and will not again until 5290. It is believed that Pholus originated as a Kuiper belt object.
It was discovered by David L. Rabinowitz, then of the University of Arizona's Spacewatch Project, and named after Pholus, the brother of the mythological Chiron, after which 2060 Chiron was named in order to follow the tradition of naming this class of outer planet crossing objects after Centaurs.
Pholus was the second centaur type asteroid to be discovered and was quickly found to be quite red in color, for which it has been occasionally nicknamed "Big Red". The color has been speculated to be due to organic compounds on its surface (Wilson, et al., 1994).
The surface composition of Pholus has been estimated from its reflectance spectrum using two spatially segregated components (Cruikshank, et al., 1998): dark amorphous carbon and an intimate mixture of water ice, methanol ice, olivine grains, and complex organic compounds (tholins). The carbon black component was used to match the low albedo of the object.
Unlike the first Centaur, 2060 Chiron, Pholus has shown no signs of cometary activity.
The diameter of Pholus is estimated to be 185±16 km [2].
[edit] References
- ^ a b c "JPL Small-Body Database Browser: 5145 Pholus (1992 AD)" (2008-05-27 last obs). Retrieved on 2008-09-01.
- ^ Tegler, Stephen C. (2006-01-26). "Kuiper Belt Object Magnitudes and Surface Colors". Retrieved on 2006-11-05.
- Wilson PD, Sagan C, Thompson WR (1994). "The organic surface of 5145 Pholus: constraints set by scattering theory". Icarus 107: 288–303. doi:. PMID 11539180
- Cruikshank DP, and 14 colleagues (1998). "The Composition of Centaur 5145 Pholus". Icarus 135: 389–407. doi:.
[edit] External links
- Orbital simulation from JPL (Java) / Ephemeris
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