Glossary Item - Neptune

Neptune

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 Sun	Length of Day	Length of Year	Radius	Mass

30.069 AU	16.1 hours	164.79 years	24,764 km	1.02*10²⁶ kg

Known Satellites

Name	Distance from Neptune	Rotational Period	Orbital Period	Radius

Naiad	48,230 km	-unknown-	0.294396 days	29 km

Thalassa	50,070 km	-unknown-	0.311485 days	40 km

Despina	52,530 km	-unknown-	0.334655 days	74 km

Galatea	61,950 km	-unknown-	0.428745 days	79 km

Larissa	73,550 km	-unknown-	0.554654 days	100 km

Proteus	117,650 km	-unknown-	1.122315 days	210 km

Triton	354,760 km	5.8768541 days	5.8768541 days	1,352 km

Nereid	5,513,400 km	-unknown-	360.13619 days	170 km

S/2002 N1	15,686,000 km	-unknown-	1,874.8 days	24 km

S/2002 N2	22,452,000 km	-unknown-	2,918.9 days	24 km

S/2002 N3	22,580,000 km	-unknown-	2,982.3 days	24 km

S/2002 N4	46,570,000 km	-unknown-	8,863.1 days	30 km

Psamathe	46,738,000 km	-unknown-	9,136.1 days	14 km

Planetary and Satellite Data: NASA's Solar System Explorer