Neptune 101 | National Geographic

(Mysterious music)

[Narrator] Along the dark edges of the Solar System, it floats. Anchored by a star but barely graced by its warmth, this traveler drifts alone, as deceptively calm and elusive as the deep blue sea. Neptune is the eighth planet from the Sun.

At about 30 times the distance between our star and the Earth, or 30 astronomical units, Neptune is the most distant planet in our Solar System. This distance creates the longest orbit of the eight worlds, about 165 years, with the seasons lasting little over 40 Earth years each. Being so far away from the heat and light of the Sun, Neptune is cold, dark, and icy.

At its heart is a solid core about 1.5 times the size of Earth. Making up about 45% of the planet's mass, the core is made of water ice and silicate rock. The rest of the planet is believed to be a hot pressurized ocean of water, methane, and ammonia ices surrounded by a layer of clouds.

These clouds, predominantly made of hydrogen and helium, include traces of methane, which give this ocean world its rich blue color. While the clouds create a cool, calm veneer from afar, up close, they are whipped around by the most severe weather in the Solar System. Winds on the planet reach speeds of over 1,200 miles per hour, nearly five times faster than the strongest winds recorded on Earth.

In fact, the winds are so powerful that they break the sound barrier. Drifting high above this windy ice giant is a quiet ecosystem of rings and satellites. Six rings encircle the planet, with some containing ring arcs, or clusters of dust particles in a ring.

Also revolving around the planet are 14 known moons, with the largest called Triton. Named after the son of the ancient Greek sea god, Triton has ice volcanoes and may even contain a subsurface ocean. Much is left to be discovered about Neptune, its rings, and its moons.

Only one spacecraft, Voyager 2, has visited these cosmic bodies, but future missions to this mysterious icy world would have even more stories to tell.