5145 Pholus
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| Discovery | |
|---|---|
| Discovered by: | Spacewatch (David L. Rabinowitz) |
| Discovery date: | January 9, 1992 |
| Alternative names: | 1992 AD |
| Minor planet category: | Centaur, Asteroid |
| Orbital characteristics | |
| Epoch November 26, 2005 (JD 2453700.5) | |
| Aphelion distance: | 4806.533 Gm (32.130 AU) |
| Perihelion distance: | 1306.224 Gm (8.732 AU) |
| Semi-major axis: | 3056.379 Gm (20.431 AU) |
| Eccentricity: | 0.573 |
| Orbital period: | 33730.363 d (92.35 a) |
| Avg. orbital speed: | 6.01 km/s |
| Mean anomaly: | 55.230° |
| Inclination: | 24.685° |
| Longitude of ascending node: | 119.332° |
| Argument of perihelion: | 355.225° |
| Physical characteristics | |
| Dimensions: | 185±16 km [1] |
| Mass: | ~6.6×1018 kg |
| Mean density: | 2.0? g/cm³ |
| Equatorial surface gravity: | ~0.052 m/s² |
| Escape velocity: | ~0.098 km/s |
| Rotation period: | 9.983 hours |
| Albedo: | 0.046±0.02 |
| Temperature: | ~62 K |
| Spectral type: | (red) B-V=1.19; V-R=0.78 [1] |
| Absolute magnitude: | 7.64 |
5145 Pholus ("FOE luss") is a Centaur in an eccentric orbit, with a perihelion near the orbit of Saturn and aphelion near the orbit of Neptune. It is believed to have originated as a Kuiper belt object.
It was discovered by David L. Rabinowitz, then of the University of Arizona's Spacewatch Project, and named by him after Pholus, the brother of the mythological Chiron, after which 2060 Chiron was named.
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
- ^ Tegler, Stephen C. (2006-01-26). Kuiper Belt Object Magnitudes and Surface Colors. Retrieved on November 5, 2006.
- Wilson PD, Sagan C, Thompson WR (1994). "The organic surface of 5145 Pholus: constraints set by scattering theory". Icarus 107: 288-303. PMID 11539180
- Cruikshank DP, and 14 colleagues (1998). "The Composition of Centaur 5145 Pholus". Icarus 135: 389-407.
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