Janus (moon)
Janus as imaged by Cassini on 7 April 2010: highest-resolution full-disk image to date | |
| Discovery | |
|---|---|
| Discovered by | Audouin Dollfus |
| Discovery date | 15 December 1966 |
| Designations | |
Designation | Saturn X |
| Pronunciation | /ˈdʒeɪnəs/ |
Named after | Jānus |
| Adjectives | Janian /ˈdʒeɪniən/ |
| Orbital characteristics | |
| Epoch 31 December 2003 (JD 2 453 005.5) | |
| 151460±10 km | |
| Eccentricity | 0.0068 |
| 0.694660342 d | |
| Inclination | 0.163°±0.004° to Saturn's equator |
| Satellite of | Saturn |
| Group | Co-orbital with Epimetheus |
| Physical characteristics | |
| Dimensions | 203.4 × 185.8 × 149.0 km (± 1.8 × 0.6 × 0.6 km): 2 |
| 178.0±1.0 km: 2 | |
| Volume | 2953010±950 km3: 4 |
| Mass | (1.89388±0.00028)×1018 kg |
Mean density | 0.6413±0.0002 g/cm3: 4 |
| 0.0111–0.0169 m/s2: 3 | |
| 0.05 km/s at longest axis to 0.058 km/s at poles | |
| synchronous | |
| 0° | |
| Albedo | 0.71±0.02 (geometric) |
| Temperature | 76 K |
Janus /ˈdʒeɪnəs/ is an inner satellite of Saturn. It is also known as Saturn X. It is named after the mythological Janus. This natural satellite was first identified by Audouin Dollfus on December 15, 1966, although it had been unknowingly photographed earlier by Jean Texereau. Further observations led to the realization that Janus shares a unique orbital relationship with another moon, Epimetheus. The discovery of these two moons' peculiar co-orbital configuration was later confirmed by Voyager 1 in 1980.