The seventh planet from the Sun and the third largest of the gas giants (narrowly beating out Neptune) with a diameter about four times that of Earth. Uranus was discovered by William Herschel in 1781. Others had seen it earlier – at its brightest it is just visible to the naked eye – but had taken it to be a star because it doesn't move perceptibly from one night to the next. Uranus's most extraordinary feature is the tilt of its axis – almost 98° (or 82° if it is taken to be retrograde), so that the planet effectively spins around on its side. As a result, for part of its orbit, one pole continually faces the Sun while the other is in total darkness. Half an orbit later, the roles (and poles) are reversed. In between, the Sun rises and sets around the equator normally. For Uranus to be in such a position, it was almost certainly struck a formidable blow by another massive object. Since the plane containing its 13 rings (see Uranus, rings) and 27 known moons (see Uranus, moons) is similarly tilted, this impact presumably took place during or shortly after the accretionary phase of the planets. The atmosphere of Uranus is composed of hydrogen (83%), helium (15%), methane (2%), and trace amounts of acetylene and other hydrocarbons. Its bluish hue stems from an upper methane haze that absorbs strongly at red wavelengths leaving a featureless blue planet in our telescopes.
Uranus - DetailsLast Updated on 2009-03-17 00:00:00Uranus is the seventh planet from the Sun and the third largest of the gas giants (narrowly beating out Neptune) with a diameter about four times that of Earth. Uranus was discovered by William Herschel in 1781. Others had seen it earlier – at its brightest it is just visible to the naked eye – but had taken it to be a star because it doesn't move perceptibly from one night to the next. The earliest recorded sighting was in 1690 when John Flamsteed catalogued it as 34 Taurus. William Herschel originally called it Georgium Sidus (George’s Star) in honor of King George III, while French astronomers began calling it Herschel. It was Johann Bode who proposed the name Uranus, after the Greek god of the heavens, but this didn't come into common usage until around 1850. Image: "Uranus, Rings and Satellites."
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Uranus - OverviewLast Updated on 2008-12-22 00:00:00Once considered one of the blander-looking planets, Uranus (pronounced YOOR un nus) has been revealed as a dynamic world with some of the brightest clouds in the outer solar system and 11 rings. The first planet found with the aid of a telescope, Uranus was discovered in 1781 by astronomer William Herschel. The seventh planet from the Sun is so distant that it takes 84 years to complete one orbit. Uranus, with no solid surface, is one of the gas giant planets (the others are Jupiter, Saturn, and Neptune).
The atmosphere of Uranus is composed primarily of hydrogen and helium, with a small amount of methane and traces of water and ammonia. Uranus gets its blue-green color from methane gas. Sunlight is reflected from Uranus' cloud tops, which lie beneath a layer of methane gas. As the reflected sunlight passes back through this layer, the methane gas absorbs the red portion of the light,... More »
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