Neptune is the outermost of the gas giant planets. It has an equatorial diameter of 49,500 kilometers and orbits the Sun once every 165 Earth years. A day on Neptune lasts 16 hours, 6.7 minutes. Neptune has only 8 moons, and six of those were discovered by the Voyager spacecraft in 1989. Neptune was discovered on September 23, 1846 by Johannes Gottfried Galle and Louis d'Arrest, using mathmatical predictions from Urbain Jean Joseph LeVerrier. The inner layers of Neptune are composed of molten rock, liquid ammonia, water, and methane. The methane gas is what gives Neptune its blue color.
Neptune is a dynamic planet, producing large storms like those of Jupiter. The largest was the Great Dark Spot, which was the size of the Earth. The Great Dark Spot has mysteriously dissapered since Voyager's visit to Neptune in 1989. The strongest winds in the Solar System can be found on Neptune, reaching speeds up to 2,000 kilometers per hour. Neptune has a set of four narrow rings which are very faint. It is believed the rings formed from material blasted from the planet's moons by small meteroites.
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