Neptune
The eighth planet from the Sun
The farthest planet, thirty times Earth's distance from the Sun, Neptune was found by calculation before anyone saw it: Urbain Le Verrier worked out where an unseen planet had to be to pull Uranus off its path, and Johann Galle found it there on 23 September 1846. Its year lasts 165 of ours; in 2011 it completed its first orbit since its discovery.
An ice giant a little smaller than Uranus but heavier, it has the fastest winds in the Solar System, up to 2,100 km/h. Its colour here is its real one, a pale blue barely bluer than Uranus: the deep blue of Voyager 2's 1989 images was enhanced. The Great Dark Spot those images made famous had vanished by 1994, so it is not shown.
Key figures
- Diameter
- 49,528 km, 3.88 × Earth
- Mass
- 17.1 × Earth
- Gravity at the 1-bar level
- 11.27 m/s², 1.15 × Earth's
- Rotation period
- 16 h 6 min
- Axial tilt
- 28.32°
- One orbit of the Sun
- 164.8 years
- Mean distance from the Sun
- 4.515 billion km
- Temperature at the 1-bar level
- -201 °C
- Fastest winds
- up to 2,090 km/h
- Atmosphere
- 80% hydrogen, 19% helium, 1.5% methane
- Moons
- 16