User:Arkuat/Sandbox
From Wikipedia, the free encyclopedia
Compare to Phoebe
For other meanings see Proteus.
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| Discovery | |||||||
|---|---|---|---|---|---|---|---|
| Discovered by | Reitsema, Hubbard, Lebofsky, Tholen | ||||||
| Discovered on | May 24, 1981 | ||||||
| Orbital characteristics (Epoch J2000) | |||||||
| Semi-major axis | km (AU) |
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| Ortbital circumference | Tm (AU) | ||||||
| Eccentricity | number | ||||||
| Perihelion | km (AU) | ||||||
| Aphelion | km (AU) | ||||||
| Orbital period | d (other units, such as Julian years) | ||||||
| Synodic period | d (a) (w/respect to Earth) |
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| Avg. orbital speed | km/s | ||||||
| Max. orbital speed | km/s | ||||||
| Min. orbital speed | km/s | ||||||
| Inclination (to Ecliptic) | ° (° to Sun's equator) |
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| Longitude of the ascending node |
decimal ° (° ' ") | ||||||
| Argument of the perihelion |
decimal ° (° ' ") | ||||||
| Satellite of | Neptune | ||||||
| Physical characteristics | |||||||
| Mean diameter | 420 km (440 × 416 × 404) | ||||||
| Equatorial diameter | km (Earth units) | ||||||
| Polar diameter | km (Earth units) | ||||||
| Oblateness | number | ||||||
| Surface area | km2 (Earth units) | ||||||
| Volume | km3 (Earth units) | ||||||
| Mass | 5.0×1019 kg | ||||||
| Mean density | g/cm3 | ||||||
| Surface gravity | m/s2 (gees) | ||||||
| Escape velocity | km/s | ||||||
| Rotation period | d (h) | ||||||
| Rotation velocity | km/h (m/s) (at the equator) | ||||||
| Obliquity | ° | ||||||
| Right ascension of North pole |
° (h min s) | ||||||
| Declination | ° | ||||||
| Albedo | number | ||||||
| Surface temperature |
|
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| Atmospheric characteristics | |||||||
| Pressure | kPa | ||||||
| most common | % | ||||||
| next-most-common | % | ||||||
| etcetera | % | ||||||
Proteus (proe'-tee-us, Greek Πρωτέας) is one of Neptune's moons. It is named after Proteus, the shape-changing sea god in Greek mythology. It is also designated Neptune VIII.
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[edit] Discovery
Proteus was first discovered by Harold J. Reitsema, William B. Hubbard, Larry A. Lebofsky, and David J. Tholen based on ground-based stellar occultation observations on May 24, 1981, and given the temporary designation S/1981 N 1 (IAUC 3608). The moon was not recovered until the Voyager 2 flyby in 1989 when it received the designation S/1989 N 1. Stephen P. Synnott and Bradford A. Smith announced (IAUC 4806) its recovery on July 7, 1989, speaking only of « 17 frames taken over 21 days », which gives a discovery date of sometime before June 16.
[edit] Physical characteristics
Proteus is more than 400 kilometers in diameter, larger than Neptune's moon Nereid. However, it was not discovered by Earth-based telescopes because it is so close to the planet that it is lost in the glare of reflected sunlight. Proteus is one of the darkest objects in the solar system, as dark as soot; like Saturn's moon Phoebe, it reflects only 6 percent of the sunlight that strikes it. Proteus is very cratered showing no sign of any geological modification. It is also irregularly shaped; scientists believe Proteus is about as large as a body of its density can be without being pulled into a spherical shape by its own gravity.
[edit] Data
- Orbital radius: 117,647 km
- Estimated density: 1.3 g/cm3
- Orbital period: 1.122 days
- Orbital inclination: 0.526° (to Neptune's equator), 0.026° (to the local Laplace plane), 28.92° (to the ecliptic)
[edit] See also
- List of craters on Proteus
- Asteroid 9313 Protea
[edit] External links
| Moons of Neptune | |
|---|---|
| Naiad · Thalassa · Despina · Galatea · Larissa · Proteus · Triton · Nereid · Halimede · Sao · Laomedeia · Psamathe · Neso | |
