Prometheus (moon)
Prometheus image from Cassini (December 26, 2009)
|
|
| Discovery | |
|---|---|
| Discovered by | Collins, Voyager 1 |
| Discovery date | October, 1980 |
| Orbital characteristics | |
| Epoch 31 December 2003 (JD 2453005.5) | |
| 139380±10 km | |
| Eccentricity | 0.0022 |
| 0.612990038 d | |
| Inclination | 0.008°±0.004° to Saturn's equator |
| Satellite of | Saturn |
| Physical characteristics | |
| Dimensions | 135.6 × 79.4 × 59.4 km |
|
Mean radius
|
43.1±2.7 km |
| Volume | ≈ 340000 km3 |
| Mass | (1.595±0.015)×1017 kg |
|
Mean density
|
0.48±0.09 g/cm³ |
| 0.0013–0.0058 m/s² | |
| ≈ 0.019 km/s | |
| synchronous | |
| zero | |
| Albedo | 0.6 |
| Temperature | ≈ 74 K |
Prometheus is an inner satellite of Saturn. It was discovered in 1980 (some time before October 25) from photos taken by the Voyager 1 probe, and was provisionally designated S/1980 S 27.
In late 1985 it was officially named after Prometheus, a Titan in Greek mythology. It is also designated Saturn XVI (16). Pronunciation for Prometheus is /prəˈmiːθiəs/,prə-MEE-thee-əs; Greek: Προμηθεύς.
Prometheus is extremely elongated, measuring approximately 136 km × 79 km × 59 km (85 mi × 49 mi × 37 mi). It has several ridges and valleys and a number of impact craters of about 20 km (12 mi) diameter are visible, but it is less cratered than nearby Pandora, Epimetheus, and Janus. From its very low density and relatively high albedo, it is likely that Prometheus is a very porous icy body. There is a lot of uncertainty in these values, however, and so this remains to be confirmed.
Prometheus is a shepherd satellite for the inner edge of Saturn's narrow F Ring. Pandora orbits just outside the F Ring, and has traditionally been viewed as an outer shepherd of the ring; however, recent studies indicate that only Prometheus contributes to the confinement of the ring.
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