Nereid (moon)
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| Discovery | |
|---|---|
| Discovered by | Gerard P. Kuiper[1] |
| Discovered on | May 1, 1949 |
| Orbital characteristics | |
| Semi-major axis | 5,513,400 km (0.03685 AU) |
| Eccentricity | 0.7512 |
| Periapsis | 1,353,600 km (0.00905 AU) |
| Apoapsis | 9,623,700 km (0.06433 AU) |
| Orbital period | 360.1362 d |
| Orbital velocity | max: 2.95 km/s mean: 1.12 km/s min: 0.42 km/s |
| Inclination | 5.07° (to Ecliptic) 32.55° (to Neptune's equator) 7.232° (to the local Laplace plane) |
| Is a satellite of | Neptune |
| Physical characteristics | |
| Diameter | 340 km |
| Mass | 3.1×1019 kg |
| Mean density | 1.5 g/cm3 |
| Rotation period | 0.48 d (11 h 31 min)[2] |
| Axial tilt | ? |
| Albedo | 0.14 |
| Surface temp. | ~51 K mean (estimate) |
| Atmosphere | none |
Nereid (neer'-ee-id [UK, US] or nerr'-ee-id [UK], IPA: [ˈnɪriɪd], IPA: [ˈnɛriɪd], Greek Νηρηΐδα), or Neptune II, is a moon of Neptune.
Nereid was discovered on 1 May 1949 by Gerard P. Kuiper. It is named after the Nereids, sea-nymphs of Greek mythology.
It was the outermost of Neptune's known moons for a long time (S/2002 N 1 through Psamathe have since taken that honour), and is the third largest, with a diameter of 340 km. Its orbit averages 5,513,400 km in radius, but is highly eccentric and varies from 1,353,600 to 9,623,700 kilometres. This is the most highly eccentric orbit of any known satellite in the solar system. The unusual orbit suggests that it may be a captured asteroid or Kuiper belt object, or possibly that it was perturbed during the capture of Neptune's largest moon Triton. Very little else is known of Nereid.
Nereid was too far to be properly imaged by the Voyager 2 probe when it visited the Neptune system in 1989. Photos sent back show only its highly irregular shape as no surface features could be seen at the resolution available.
[edit] References
- ^ Gerard P. Kuiper (1949). "The second satellite of Neptune". Publications of the Astronomical Society of the Pacific 61: 175–176.
- ^ T. Grav, M. Holman, J.J. Kavelaars (2003). "The Short Rotation Period of Nereid". The Astrophysical Journal 591: 71–74.
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| Naiad · Thalassa · Despina · Galatea · Larissa · Proteus Triton Nereid · S/2002 N 1 · S/2002 N 2 · S/2002 N 3 · Psamathe · S/2002 N 4 |
| See also: Neptune Trojans · Rings of Neptune |
