Solar system · Neptune

Where is Neptune right now?

Neptune, a deep blue planet with faint cloud bands, drawn in Exo-View

Neptune is the farthest planet from the Sun, 30 times the Earth's distance, and takes 165 years to go round once. It is a deep blue ice giant with the fastest winds in the solar system, and it was found not by looking but by working out where it must be. Exo-View puts it where it is at this moment.

Fly to Neptune See every planet

Orbit: 164.8 years
Distance from the Sun: 30.1 AU on average, about 4.5 billion km
Width: 49,244 km, nearly four Earths
Day: About 16 hours
Winds: Up to about 2,100 km/h, faster than sound at its cold temperatures
Temperature: About −214 °C
Moons: Sixteen known; the largest is Triton

Found with a pencil

By the 1840s Uranus was not following the orbit that Newton's laws predicted, and astronomers suspected that the pull of another, unseen planet was tugging it. Urbain Le Verrier in France and John Couch Adams in England each worked out where it should be. On 23 September 1846 Johann Galle at the Berlin Observatory looked where Le Verrier had pointed and found Neptune within a degree of the spot. It was seen by a telescope, but found by mathematics.

A year of 165 Earth years

Neptune completed its first orbit since its discovery in July 2011. It is too faint to see with the naked eye and shows in a small telescope as a tiny blue disc. Its colour comes from methane in its air, with another ingredient no one has identified. Despite its distance from the Sun, it gives off more heat than it receives, and that heat drives winds that tear along at up to about 2,100 km/h.

Triton, the captured moon

Triton, Neptune's large moon, goes round it backwards, against the planet's spin, which is a sign that it did not form there: it is probably a dwarf planet from the Kuiper Belt that Neptune captured. Triton has geysers of nitrogen, and it is slowly spiralling in towards Neptune. Voyager 2, in August 1989, is the only craft that has visited.

In Exo-View

The button below flies from the Sun to Neptune. Run the clock forward and the planet barely moves, which is the point: its year is 165 of ours.