Quick Facts Mythology Pluto's Orbit Composition The Great Dark Spot Rings

The Mystic

Quick Facts:
Neptune is the eighth planet from the Sun and the fourth largest.
Neptune's winds are the fastest in the solar system, reaching 2000 km/hour.
Neptune's blue color is the result of the absorption of red light by methane in the atmosphere.
Distance from the Sun: 4,504,000,000 km (2,792,000,000 miles or 30.06 AU)
Period of Revolution: 164.8 years
Diameter: 49,532 km (27,700 miles)
Mass: 1.0247e26 kg
Satellites: 8- Naiad, Thalassa, Despina, Galatea, Larissa, Proteus, Triton, and Nereid.

Mythology:
In Roman mythology Neptune was the god of the Sea. The Greek equivalent of Neptune was Poseidon.

Pluto's Orbit:
Because Pluto's orbit is so eccentric, it sometimes crosses the orbit of Neptune. Since 1979 Neptune has actually been the most distant planet from the Sun; Pluto will again be the most distant in 1999.

Composition:
Neptune (like Uranus) is composed of various ices and rock with about 15% hydrogen and a little helium. It may not have a distinct internal layering but rather to be more or less uniform in composition. There is most likely a small core of rocky material. Its atmosphere is mostly hydrogen and helium with a small amount of methane.

The Great Dark Spot:
Neptune's most prominent feature is the Great Dark Spot in the southern hemisphere. It is about half the size as Jupiter's Great Red Spot. Neptune's winds blew the Great Dark Spot westward at 300 meters/second (700 mph). Neptune also has a smaller dark spot in the southern hemisphere and a small irregular white cloud that zips around Neptune every 16 hours known as "The Scooter".
More recent observations, by HST, of  Neptune in 1994 showed that the Great Dark Spot had disappeared. It had either simply dissipated or is currently being masked by other aspects of the atmosphere. A few months later HST discovered a new dark spot in Neptune's northern hemisphere. This indicates that Neptune's atmosphere changes rapidly, perhaps due to slight changes in the temperature differences between the tops and bottoms of the clouds.

Rings:
Like Saturn, Neptune also has rings. One of the rings appears to have a curious twisted structure like licorish candy. Like Uranus and Jupiter, Neptune's rings are very dark but their composition is unknown. Neptune's rings have been given names: the outermost is Adams (which contains three prominent arcs now named Liberty, Equality and Fraternity), next is an unnamed ring coorbital with Galatea, then Leverrier (whose outer extensions are called Lassell and Arago), and finally the faint but broad Galle.