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Neptune has eight known satellites, two of which can be observed from Earth. The largest and brightest is Triton. It was discovered in 1846 and is only slightly smaller than Earth’s moon (2705 km in diameter). Triton has a retrograde orbit, which means it orbits Neptune the opposite way to Neptune's rotation. Triton has an atmosphere of nitrogen with a small amount of methane.

Triton is slowly spiralling towards Neptune. In 10 to 100 million years is expected to be so close to Neptune that it will be pulled apart and form a sixth ring. Not much is known about Neptune’s other 7 satellites as they are very small.

Some Astronomers think that Pluto could have been one of Neptune’s moons that escaped it’s orbit. some even think that Pluto could still be one of Neptune’s moons due to the crossing of their orbits of the sun which leaves Neptune the furthest planet from the sun for about 2 years.

Satellite		Radius (km)		Mass (kg)		Discoverer and Date

Naiad			29			?			Voyager 2  	1989

Thalassa		40			?			Voyager 2  	1989

Despina			74			?			Voyager 2  	1989

Galatea			79			?			Voyager 2	1989
Larissa			96			?			Voyager 2 	1989

Proteus			209			?			Voyager 2	1989

Triton			1350			2.14*1022		Lassel		1846

Nereid			170			?			Kuiper		1949