 Despina as seen by Voyager 2 (smeared horizontally) | |
| Discovery | |
|---|---|
| Discovered by | Stephen P. Synnott[1] and Voyager Imaging Team |
| Discovered in | July 1989 |
| Orbital characteristics[2] | |
| | |
| Semi-major axis | 52 526 ± 1 km |
| Eccentricity | 0.0002 ± 0.0002 |
| Orbital period | 0.33465551 ± 0.00000001 d |
| Inclination | 0.216 ± 0.014° (to Neptune equator) 0.06° (to local Laplace plane) |
| Is a satellite of | Neptune |
| Physical characteristics | |
| Dimensions | 180×148×128 km[3][4] |
| Mean radius | 75 ± 3 km[5] |
| Mass | ~2.1 × 1018 kg (based on assumed density) |
| Mean density | ~1.2 g/cm3 (estimate) |
| Rotation period | assumed synchronous |
| Axial tilt | ~zero presumably |
| Albedo (geometric) | 0.09[3][4] |
| Surface temp. | ~51 K mean (estimate) |
| Atmosphere | none |
Despina (pronounced /dɨˈspiːnə/ dis-PEE-nə, sometimes /dɨˈspaɪnə/ dis-PYE-nə, or as in Latin Despœna, Greek Δέσποινα), also known as Neptune V, is the third closest inner satellite of Neptune. It is named after Despoina, a nymph who was a daughter of Poseidon and Demeter.
Despina was discovered in late July, 1989 from the images taken by the Voyager 2 probe. It was given the temporary designation S/1989 N 3'.[6] The discovery was announced (IAUC 4824) on August 2, 1989, but the text only talks of "10 frames taken over 5 days", giving a discovery date of sometime before July 28. The name was given on 16 September 1991.[7]
Despina is irregularly shaped and shows no sign of any geological modification. It is likely that it is a rubble pile re-accreted from fragments of Neptune's original satellites, which were smashed up by perturbations from Triton soon after that moon's capture into a very eccentric initial orbit.[8]
Despina's orbit lies close to but outside of the orbit of Thalassa and just inside the Le Verrier ring. As it is also below Neptune's synchronous orbit radius, it is slowly spiralling inward due to tidal decceleration and may eventually impact Neptune's atmosphere, or break up into a planetary ring upon passing its Roche limit due to tidal stretching.
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