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Cool Facts about Uranus
By Joe Rao
Special to SPACE.com
posted: 30 June 2005
06:37 am
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Untitled DocumentUranus lies nearly 2 billion miles (3.2 billion kilometers) from the Sun and is the seventh planet out (only Neptune and Pluto are farther). It has a diameter of about 32,000 miles (51,500 kilometers) and, according to flyby magnetic data from Voyager 2 in 1986, has a rotation period of 17.4 hours. At last count, the planet has more than 20 moons [another was just announced last week]. Along the plane of the planets equator is also a complex of nine narrow, nearly opaque rings, which were discovered in 1978. Uranus likely has a rocky core, surrounded by a liquid mantle of water, methane, and ammonia, all encased in an atmosphere of hydrogen and helium. A bizarre feature is how far over Uranus is tipped. Its north pole -- representing the planet's axis of rotation -- lies 98 degrees from being directly up and down to its orbit plane, which means the planet is essentially on its side in relation to the Sun. Thus, its seasons are extreme: when the Sun rises at its north pole, it stays up for 42 Earth years; then it sets and the north pole is in darkness for 42 Earth years. Sir William Herschel discovered Uranus on March 13, 1781, noting that it was moving slowly through the constellation Gemini. Initially, however, Herschel thought he had discovered a new comet.
Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for The New York Times and other publications, and he is also an on-camera meteorologist for News 12 Westchester, New York.
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