One day on Neptune takes about 16 hours (the time it takes for Neptune to rotate or spin once). And Neptune makes a complete orbit around the Sun (a year in Neptunian time) in about 165 Earth years (60,190 Earth days).

Voyager 2 is the only spacecraft to have visited Neptune. No spacecraft has orbited this distant planet to study it at length and up close.

Jan 9, 2025 · Neptune is the eighth and most distant planet from the Sun. It’s the fourth largest, and the first planet discovered with math.

Jan 9, 2025 · NASA’s real-time science encyclopedia of deep space exploration. Our scientists and far-ranging robots explore the wild frontiers of our solar system.

Dec 14, 2012 · Voyager 2 is the only spacecraft to have visited Uranus and Neptune. At closest approach, the spacecraft came within 50,600 miles (81,500 km) of Uranus's cloud tops. The thousands of images and reams of scientific data Voyager 2 sent back revealed a complex system of rings, moons, and an unusual magnetosphere.

Proteus orbits Neptune about every 27 hours. Proteus is irregularly shaped and heavily cratered, but it shows no sign of geological modification. Circling the planet in the same direction as Neptune rotates, Proteus remains close to Neptune's equatorial plane.

NASA’s real-time science encyclopedia of deep space exploration. Our scientists and far-ranging robots explore the wild frontiers of our solar system.

Oct 26, 2000 · It discovered that the planet is made up of about 83 percent hydrogen, 15 percent helium and two percent methane. This is the latest in a series of evaluations of composition data from the gas planets, Jupiter, Saturn, Uranus and Neptune, which have increasingly shown that their makeup is very close to the amounts of hydrogen and helium in the sun.

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Jan 29, 2001 · However, since Voyager 1 did make it to Saturn and perform a close examination of its largest moon Titan, Voyager 2 was given the go-ahead to Uranus and eventually Neptune in 1989 (it should be noted that Voyager 2 also survived being shut off in 1981 to allegedly save some bucks by the Reagan Administration, I kid you not).