Depth 11 · Ice giant

Neptune

Neptune is the eighth and farthest known planet from the Sun, a dark, cold ice giant with the fastest winds measured in the solar system. It was the first planet located through mathematical prediction rather than by scanning the sky.

Fact sheet

Type

Ice giant planet

Distance

About 4.5 billion km (2.8 billion miles), or 30 AU, from the Sun on average

Size

Equatorial diameter about 49,528 km (30,775 miles), about four times as wide as Earth

Discovered

Discovered 23 September 1846 by Johann Galle, using Urbain Le Verrier's prediction

On the voyage

Depth 11, in the Outer Sol section of the route, between Uranus and Triton

Things to know

• Urbain Le Verrier predicted Neptune's position from wobbles in Uranus's orbit, and Johann Galle found it in 1846 on his first night of searching. NASA
• Winds on Neptune top 2,000 km/h (1,200 mph), about three times faster than Jupiter's strongest winds. NASA
• One orbit of the Sun takes about 165 Earth years, so each of Neptune's four seasons lasts more than 40 years. NASA
• Voyager 2 came within about 4,800 km (2,980 miles) of Neptune's cloud tops in 1989, the closest of its four planetary flybys. NASA
• A storm called the Great Dark Spot, big enough to hold Earth, was seen in 1989 but has since vanished while new storms have appeared. NASA

Missions

Voyager 2 is the only spacecraft to have visited Neptune, flying past on 25 August 1989.

Sources

• NASA – Neptune Facts
• NSSDC – Neptune Fact Sheet
• NASA – Voyager 2