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Nereid (moon)
From Wikipedia, the free encyclopedia
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| Discovery | |
|---|---|
| Discovered by: | Gerard P. Kuiper[1] |
| Discovery date: | May 1, 1949 |
| Orbital characteristics | |
| Periapsis: | 1,353,600 km (0.00905 AU) |
| Apoapsis | 9,623,700 km (0.06433 AU) |
| Semi-major axis: | 5,513,400 km (0.03685 AU) |
| Eccentricity: | 0.7512 |
| Orbital period: | 360.1362 d |
| Avg. orbital speed: | 1.12 km/s |
| Inclination: | 5.07° (to Ecliptic) 32.55° (to Neptune's equator) 7.232° (to the local Laplace plane) |
| Satellite of: | Neptune |
| Physical characteristics | |
| Mean radius: | 170 km |
| Mass: | 3.1×1019 kg[citation needed] |
| Mean density: | 1.5 g/cm3 |
| Rotation period: | 0.48 d (11 h 31 min)[2] |
| Albedo: | 0.14 |
| Temperature: | ~51 K mean (estimate) |
Nereid (pronounced /ˈnɪəriɪd/ [UK, US], or /ˈnɛriɪd/ [UK]; Greek Νηρηΐδα), or Neptune II, is a moon of Neptune.
Nereid was discovered on 1 May 1949 by Gerard P. Kuiper, who proposed the name in the report of his discovery. It is named after the Nereids, sea-nymphs of Greek mythology.
It was the outermost of Neptune's known moons for a long time (Halimede through Neso 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. For a long time this was the most highly eccentric orbit of any known satellite in the solar system, but it has recently been superseded by Bestla, a recently discovered moon of Saturn. 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, and no surface features could be seen at the resolution available.
- ^ 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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| Generally listed in increasing distance from Neptune. |
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|---|---|---|
| Moons | Naiad · Thalassa · Despina · Galatea · Larissa · Proteus · Triton · Nereid · Halimede · Sao · Laomedeia · Psamathe · Neso |  |
| Characteristics | Rings of Neptune · Great Dark Spot | |
| Discovery | John Couch Adams · Johann Gottfried Galle · William Lassell · Urbain Le Verrier | |
| Exploration | Voyager program · Voyager 2 | |
| Neptune Trojans | 2001 QR322 · 2004 UP10 · 2005 TN53 · 2005 TO74 · 2006 RJ103 · 2007 RW10 | |
| Other | Neptune-crosser asteroid · Neptune in fiction | |