Hyperion (moon)
 |
|
| Discovery | |
|---|---|
| Discovered by | |
| Discovery date | 16 September 1848 |
| Designations | |
| Saturn VII | |
| Adjectives | Hyperionian |
| Orbital characteristics | |
| 1,481,009 km (920,256 mi) | |
| Eccentricity | 0.1230061 |
| 21.276 d | |
| Inclination | 0.43° (to Saturn's equator) |
| Satellite of | Saturn |
| Physical characteristics | |
| Dimensions | 360.2 km × 266 km × 205.4 km (223.8 mi × 165.3 mi × 127.6 mi) |
|
Mean radius
|
135 km (84 mi) |
| Mass | (5.6199±0.05)×1018 kg |
|
Mean density
|
0.544±0.050 g/cm3 |
| 0.017–0.021 m/s2 depending on location | |
| 45–99 m/s depending on location. | |
| chaotic | |
| variable | |
| Albedo | 0.3 |
| Temperature | 93 K (−180 C) |
| 14.1 | |
Hyperion (/haɪˈpɪəriən/ hy-PEER-ee-ən; Greek: Ὑπερίων), also known as Saturn VII (7), is a moon of Saturn discovered by William Cranch Bond, George Phillips Bond and William Lassell in 1848. It is distinguished by its irregular shape, its chaotic rotation, and its unexplained sponge-like appearance. It was the first non-round moon to be discovered.
The moon is named after Hyperion, the Titan god of watchfulness and observation – the elder brother of Cronus, the Greek equivalent of Saturn – in Greek mythology. It is also designated Saturn VII. The adjectival form of the name is Hyperionian.
Hyperion's discovery came shortly after John Herschel had suggested names for the seven previously-known satellites of Saturn in his 1847 publication Results of Astronomical Observations made at the Cape of Good Hope.William Lassell, who saw Hyperion two days after William Bond, had already endorsed Herschel's naming scheme and suggested the name Hyperion in accordance with it. He also beat Bond to publication.
Hyperion is one of the largest bodies known to be highly irregularly shaped (non-ellipsoidal, i.e. not in hydrostatic equilibrium) in the Solar System. The only larger moon known to be irregular in shape is Neptune's moon Proteus. Hyperion has about 15% of the mass of Mimas, the least massive known ellipsoidal body. The largest crater on Hyperion is approximately 121.57 km (75.54 mi) in diameter and 10.2 km (6.3 mi) deep. A possible explanation for the irregular shape is that Hyperion is a fragment of a larger body that was broken up by a large impact in the distant past. A proto-Hyperion could have been 350–1,000 km (220–620 mi) in diameter. Over about 1,000 years, ejecta from a presumed Hyperion breakup would have impacted Titan at low speeds, building up volatiles in the atmosphere of Titan.
...
Wikipedia