larger image and description | |||||||
Discovery | |||||||
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Discovered by | Urbain Leverrier John Couch Adams Johann Galle |
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Discovered in | 1846 | ||||||
Orbital characteristics | |||||||
Mean radius | 4.5043×109 km | ||||||
Eccentricity | 0.0097 | ||||||
Revolution period | 164y 288d 13h | ||||||
Synodic period | 367.5 days | ||||||
Avg. Orbital Speed | 5.5 km/s | ||||||
Inclination | 1.774° | ||||||
Number of satellites | 11 | ||||||
Physical characteristics | |||||||
Equatorial diameter | 49572 km | ||||||
Surface area | 7.65×109[?] km2 | ||||||
Mass | 1.024×1026 kg | ||||||
Mean density | 1.64 g/cm3 | ||||||
Surface gravity | 11.0 m/s2 | ||||||
Rotation period | 16h 6.5m | ||||||
Axial tilt | 28.31° | ||||||
Albedo | 0.41 | ||||||
Escape Speed | 23.5 km/s | ||||||
Surface temp. |
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Atmospheric characteristics | |||||||
Atmospheric pressure | kPa | ||||||
Hydrogen | >84% | ||||||
Helium | >12% | ||||||
Methane | 2% | ||||||
Ammonia | 0.01% | ||||||
Ethane | 0.00025% | ||||||
Acetylene | 0.00001% |
Neptune is the eighth planet from the sun. It is a gas giant.
After the discovery of Uranus, it was noted that the orbits of Uranus, Saturn, and Jupiter were not acting according to the laws of Kepler and Newton. Adams and LeVerrier independently calculated the location of another planet, Neptune, which was located by Galle, on September 23, 1846; within 1° of where Adams and Le Verrier had predicted it to be. Later, it was noted that Galilei had observed Neptune, in 1611, but he had thought it was a star.
The internal structure resembles that of Uranus - a rocky core covered by an icy crust, buried deep under its thick atmosphere. The inner two thirds of Neptune is composed of a mixture of molten rock, water, liquid ammonia and methane. The outer third is a mixture of heated gases comprised of hydrogen, helium, water and methane. Like Uranus, and unlike the uniform composition of Jupiter and Saturn, Neptune's internal structure is thought to consist of distinct layers. Like Uranus, Neptune's magnetic field is strongly tilted relative to its rotational axis at 47° and offset at least 0.55 radii (about 13,500 kilometers) from the planet's physical center. Comparing the magnetic fields of the two planets, scientists think the extreme orientation may be characteristic of flows in the interior of the planet and not the result of Uranus' sideways orientation.
Neptune is never visible with the naked eye. With the use of a telescope it appears as a blue-green disk, similar in appearance to Uranus; the blue-green colour comes from the methane in its atmosphere. Neptune has been visited by only one spacecraft, Voyager 2, which flew by the planet on August 25, 1989.
Neptune has eleven known moons.
Name | Diameter (km) | Mass (kg) | Mean orbital radius (km) |
Orbital period |
---|---|---|---|---|
Naiad | 58 | Unknown | 48,200 | 0.294396 days |
Thalassa | 80 | Unknown | 50,000 | 0.311485 days |
Despina | 148 | Unknown | 52,600 | 0.334655 days |
Galatea | 158 | Unknown | 62,000 | 0.428745 days |
Larissa | 193 (208 × 178) | Unknown | 73,600 | 0.554654 days |
Proteus | 418 (436 × 416 × 402) | Unknown | 117,600 | 1.122315 days |
Triton | 2700 | 2.14×1022 | 354,760 | -5.87685 days |
Nereid | 340 | Unknown | 5,513,400 | 360.1362 days |
S/2002 N2* | 17,5 | Unknown | 19,556,000 | 2405.21 days |
S/2002 N3* | 17,5 | Unknown | 20,857,000 | 2649.22 days |
S/2002 N1* | 17,5 | Unknown | 21,930,000 | 2856.30 days |
* Awaiting confirmation and naming.
Solar system:
Sun - Mercury - Venus - Earth - Mars - Asteroids - Jupiter - Saturn - Uranus - Neptune - Pluto - Comets
wikipedia.org dumped 2003-03-17 with terodump