Neptune is the eighth and most distant planet from the Sun. Discovered in 1846, it is named after the Roman god of the sea. Methane in its atmosphere helps give the planet its blue appearance.
Neptune is an ice giant, a category it shares with Uranus. Its outer atmosphere is mostly hydrogen and helium with some methane, while models of its interior include water, methane and ammonia at extreme pressures. Neptune is roughly four times as wide as Earth and about 17 times as massive.
Its atmosphere has some of the fastest winds measured in the solar system, and Neptune has faint rings. Voyager 2 photographed a large storm called the Great Dark Spot during its 1989 flyby. That particular spot later disappeared; other dark storms have been observed since.
As of September 2026, NASA lists 16 known moons of Neptune. The largest, Triton, travels in a retrograde orbit, opposite Neptune’s rotation. Triton’s unusual orbit suggests that Neptune captured it long ago.
Neptune orbits about 30 times farther from the Sun than Earth does, so the sunlight there is roughly one nine-hundredth as strong. Voyager 2 remains the only spacecraft to have visited Neptune up close. Telescopes continue to study its atmosphere, rings and moons from afar.
Explore further: NASA Neptune overview and images.
