Phoebe (moon)
Cassini mosaic of Phoebe
|
|
| Discovery | |
|---|---|
| Discovered by | W.H. Pickering |
| Discovery date | 17 March 1899 & 16 August 1898 |
| Designations | |
| Saturn IX | |
| Adjectives | Phoebean |
| Orbital characteristics[1] | |
| 12.96 Gm | |
| Eccentricity | 0.1562415 |
| 550.564636 d | |
| Inclination | 173.04° (to the ecliptic) 151.78° (to Saturn's equator) |
| Satellite of | Saturn |
| Physical characteristics | |
| Dimensions | (218.8±2.8) × (217.0±1.2) × (203.6±0.6) km |
|
Mean radius
|
106.5±0.7 km |
| Mass | (8.292±0.010)×1018 kg |
|
Mean density
|
1.638±0.033 g/cm³ |
| 0.038–0.050 m/s2 | |
| ≈ 0.10 km/s | |
|
Sidereal rotation period
|
9.2735 h (9 h 16 min 25 s ± 3 s) |
| 152.14° | |
| Albedo | 0.06 |
| Temperature | ≈ 73(?) K |
Phoebe (/ˈfiːbiː/ FEE-bee; Greek: Ancient Greek: Φοίβη Phoíbē) is an irregular satellite of Saturn with a mean diameter of 213 km. It was discovered by William Henry Pickering on 17 March 1899 from photographic plates that had been taken starting on 16 August 1898 at the Boyden Observatory near Arequipa, Peru, by DeLisle Stewart. It was the first satellite to be discovered photographically.
Phoebe was the first target encountered upon the arrival of the Cassini spacecraft in the Saturn system in 2004, and is thus unusually well-studied for an irregular satellite of its size. Cassini's trajectory to Saturn and time of arrival were specifically chosen to permit this flyby. After the encounter and its insertion into orbit, Cassini did not go much beyond the orbit of Iapetus.
Phoebe is roughly spherical and has a differentiated interior. It was spherical and hot early in its history and was battered out of roundness by repeated impacts. It is thought to be a captured planetesimal from the Kuiper belt.
Phoebe was discovered by William Henry Pickering on 17 March 1899 from photographic plates that had been taken starting on 16 August 1898 at the Boyden Observatory near Arequipa, Peru, by DeLisle Stewart. It was the first satellite to be discovered photographically.
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