Neptune Was Predicted by Mathematics Before It Was Seen
Urbain Le Verrier and John Couch Adams calculated its position from irregularities in Uranus's orbit, and Johann Galle found it in Berlin in September 1846.
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Voyager 2 Is the Only Spacecraft to Visit Neptune
It flew past the planet in August 1989.
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Triton, Neptune's Largest Moon, Orbits Backward
Its retrograde orbit suggests it is a captured Kuiper Belt object, and it has geysers that spray nitrogen.
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A Year on Neptune Lasts About 165 Earth Years
It completed its first full orbit since discovery in 2011.
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Neptune Has the Fastest Winds in the Solar System
Winds on the ice giant reach roughly 2,000 kilometers per hour.