Position - eighth or ninth from the sun

Distance from sun - (nearest) 4460 million km (furthest) 4540 million km (average) 4500 million km

Minimum distance from Earth - 4310 million km

Diameter - 49,500 km

Satellites - at least 8 the largest being Triton (2700 km) which orbits Neptune backwards and is covered in ice. The others are Naiad, Thalassa, Despina, Galatea, Larissa, Proteus and Nereid.

Atmosphere - hydrogen, helium and methane

Surface Temperature down to - 210 ^oC

Length of Day (time taken to rotate once) - about 17 hours

Length of Year (time taken to go round the Sun) - 165 Earth years

Comments - It appears that Neptune is actually largely made of frozen water with an iron core. It was discovered in 1846 when astronomers calculated that another planet must exist because of it's effects on the orbits of the other planets. At the moment Neptune is the furthest planet from the Sun because of Pluto's strange orbit. Neptune is the windiest planet, with winds of up to 2,200 km per hour!

Major Features - Neptune has a thin, faint ring system which has only recently been discovered. The planet itself is rather featureless blue, but it has a feature known as the Great Dark Spot.

Seeing Neptune from Earth - Neptune can only be seen with a telescope.

Getting There - The only probe to visit Neptune so far was Voyager 2 which reached the planet after visiting Jupiter, Saturn and Uranus.