Uranus

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Uranus Seventh planet from the Sun, discovered (1781) by Sir William Herschel. Uranus is visible to the naked eye under good conditions. Through a telescope it appears as a small, featureless, greenish-blue disc. Like all the giant planets, it possesses a ring system and a retinue of satellites. Like Pluto, Uranus' axis of rotation is steeply inclined, and its poles spend 42 years in sunlight, followed by 42 years in darkness. Highly exaggerated seasonal variations are experienced by the planet and its satellites. The fly-by of the Voyager 2 probe in 1986 provides most of our knowledge of the planet. The upper atmosphere is about 83% molecular hydrogen, 15% helium, and the other 2% mostly methane. The five largest satellites were known before the Voyager encounter, which led to the discovery of 11 more. Nineteen of its 22 moons are regular satellites, orbiting in or close to Uranus' equatorial plane. They are all darkish bodies composed of ice761 and rock. The main components of Uranus' ring system were discovered in 1977, and others were imaged by Voyager.

http://lpl.arizona.edu/nineplanets/nineplanets/uranus.html; http://wr.usgs.gov

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