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Voyager 2 captured this image of Neptune in 1989.
Voyager 2 captured this image of Neptune in 1989.

Dark, cold and whipped by supersonic winds, Neptune is the last of the hydrogen and helium gas giants in our solar system. More than 30 times as far from the sun as Earth, the planet takes almost 165 Earth years to orbit our sun. In 2011 it will complete its first orbit since its discovery in 1846.

Featured Mission: Voyager 2
Most of what we know about Neptune is thanks to Voyager 2's 1989 flyby. The spacecraft also discovered six of Neptune's moons.

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Just the Facts
Orbit Size (semi-major axis):  4,498,396,441 km
Mean Radius:  24,622 km
Volume:  62,525,703,987,421 km3
Mass:  102,410,000,000,000,000,000,000,
000 kg
22 Aug 2011: 
People Spotlight
Gerard Kuiper Gerard Kuiper
Gerard Kuiper is regarded by many as the father of modern planetary science. His theories led to the discovery of the Kuiper Belt. Read More...
Mark Hofstadter - Planetary Scientist
Al Hibbs - Scientist
David Grinspoon - Museum Curator
Jeffrey Cuzzi - Research Scientist
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Last Updated: 27 Apr 2011