Proteus (moon)
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- ''There is also an asteroid called 9313 Protea.
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| Discovery | |||||||
| Discovered by | Voyager 2 Stephen P. Synnott | ||||||
| Discovered on | June 16, 1989 | ||||||
| Orbital characteristics (Epoch J2000) | |||||||
| Semi-major axis | 117,647 km (0.00079 AU) | ||||||
| Eccentricity | 0.0005 | ||||||
| Periapsis | 117,588 km | ||||||
| Apoapsis | 117,706 km | ||||||
| Orbital period | 1.122315 d | ||||||
| Orbital circumference | 739,200 km (0.005 AU) | ||||||
| Orbital velocity | max: 7.629 km/s mean: 7.625 km/s min: 7.621 km/s | ||||||
| Inclination | 28.92° (to Ecliptic) 0.526° (to Neptune's equator) 0.026° (to the local Laplace plane) | ||||||
| Satellite of | Neptune | ||||||
| Physical characteristics | |||||||
| Diameter | 436 × 416 × 402 km | ||||||
| Surface area | ~2,195,000 km² | ||||||
| Volume | ~38,177,000 km3 | ||||||
| Mass | kg | ||||||
| Mean density | 1.3 g/cm3 | ||||||
| Surface gravity | ~0.075 m/s2 (0.001 g) | ||||||
| Escape velocity | ~0.18 km/s | ||||||
| Rotation period | synchronous | ||||||
| Axial tilt | zero | ||||||
| Albedo | 0.10 | ||||||
| Surface temp. |
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| Atmospheric pressure | 0 kPa | ||||||
Discovery
Proteus was discovered from the images taken by Voyager 2 probe during the Neptune flyby in 1989. It received the temporary designation S/1989 N 1. Stephen P. Synnott and Bradford A. Smith announced (IAUC 4806) its discovery on July 7, 1989, speaking only of “17 frames taken over 21 days”, which gives a discovery date of sometime before June 16.Physical characteristics
Proteus is more than 400 kilometres in diameter, larger than Nereid, another moon of Neptune. 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. Saturn's moon Mimas has much more regular shape despite being less massive than Proteus.
See also
External links
- [IAU Circular 4806 describing the discovery of S/1989 N 1]
- [The Nine Planets – Proteus]
- [Views of the Solar System – Proteus, A Moon Of Neptune]
| Neptune (satellites) [http://encycl.opentopia.com/ edit ] |
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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-Sun Lagrangian point asteroids | Rings of Neptune |
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