Neptune
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Neptune is the eighth planet in the Solar System and the ninth body large enough for its own gravity to shape it into a spheroid. It is named after the ancient Roman god of the sea. It was discovered in 1846 on the basis of calculations made by Urbain Le Verrier and is the first and only exception to the Titius-Bode law of planetary distances from the sun. Neptune, like the other gas giants, Jupiter, Saturn, and Uranus, has rings made of ice and rock. Neptune is bluish in color and has 13 known moons, the largest of which are, in order, Triton, Proteus, and Nereid. [2]
| Neptune | |
|---|---|
 Photo of Neptune taken by Voyager 2 in 1989 | |
| Symbol | 
|
| Date of discovery | 1846 |
| Name of discoverer | Johann Gotfried Galle |
| Name origin | Roman god of the sea |
| Orbital characteristics | |
| Primary | Sun |
| Order from primary | 9 |
| Perihelion | 29.810 AU |
| Aphelion | 30.327 AU |
| Semi-major axis | 30.069 AU |
| Titius-Bode prediction | 38.8 AU |
| Circumference | 188.925 AU |
| Orbital eccentricity | 0.009 |
| Sidereal year | 164.88 a |
| Synodic year | 367.49 da (1.006 a) |
| Avg. orbital speed | 5.432 km/s |
| Inclination | 1.769° to the ecliptic |
| Rotational characteristics | |
| Sidereal day | 16.11 h (0.671 da) |
| Axial tilt | 28.32° |
| Physical characteristics | |
| Mass | 1.0243 * 1026 kg (17.14 * earth) |
| Density | 1,638 kg/m³ |
| Equatorial radius | 24,552.5 km[1] |
| Surface gravity | 11.0 m/s² (1.122 g) |
| Escape speed | 23.50 km/s |
| Surface area | 7,619,000,000 km² (14.937 * earth) |
| Mean temperature | 53 K |
| Number of moons | 13 |
| Composition | Rock and ice |
| Color | Blue |
| Albedo | 0.41 |
Neptune was visited by the Voyager 2 spacecraft in August 1989.
Notes & References