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Neptune as seen by the Voyager II spacecraft on August 14, 1989.

Neptune is the eighth planet from the sun and takes 165 years to orbit the sun once. Neptune is about 4 times larger than the Earth and is about 17 times as massive. Neptune was discovered on September 23, 1846 based on calculations done by the French astronomer Urbain LeVerrier and the English astronomer John Adams.

Neptune is also the Roman name for Poseidon, the god of the sea and earthquakes. Neptune was the son of Chronus and Rhea and carries the trident, a three pronged spear.

Planetary Data

Distance from SunLength of DayLength of YearRadiusMass
30.069 AU16.1 hours164.79 years24,764 km1.02*1026 kg

Known Satellites

NameDistance from NeptuneRotational PeriodOrbital PeriodRadius
Naiad48,227 km-unknown-0.294396 days33 km
Thalassa50,074 km-unknown-0.311485 days41 km
Despina52,526 km-unknown-0.334655 days75 km
Galatea61,953 km-unknown-0.428745 days88 km
Larissa73,548 km-unknown-0.554654 days97 km
S/2004 N1104,200 km-unknown-0.9362 days9 km
Proteus117,646 km-unknown-1.122315 days210 km
Triton354,759 km5.8768541 days5.8768541 days1,352.6 km
Nereid5,513,818 km-unknown-360.13619 days170 km
Halimede16,611,000 km-unknown-1,874.8 days31 km
Sao22,228,000 km-unknown-2,918.9 days22 km
Laomedeia23,567,000 km-unknown-2,982.3 days21 km
Psamathe48,096,000 km-unknown-9,074.3 days20 km
Neso49,285,000 km-unknown-974073 days30 km

Planetary and Satellite Data: NASA's Solar System Explorer

Citation and linking information

For questions about this page, please contact Steve Gagnon.