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Oort cloud |
Also found in: Wikipedia, Hutchinson | 0.04 sec. |
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Oort cloud: see comet comet [Gr.,=longhaired], a small celestial body consisting mostly of dust and gases that moves in an elongated elliptical or nearly parabolic orbit around the sun. Comets visible from the earth can be seen for periods ranging from a few days to several months. ..... Click the link for more information. . Oort cloudVast spherical cloud of small, icy bodies orbiting the Sun at distances ranging from about 0.3 light-year to one light-year or more that is probably the source of most long-period comets. In 1950 the Dutch astronomer Jan Hendrik Oort (1900–92) noted that no comets have orbits that would indicate an interstellar origin. He proposed that the Sun is surrounded by billions of these objects, which are only occasionally detectable when they enter the inner solar system. The Oort cloud is believed to be composed of primordial bodies dating from the formation of the solar system (see solar nebula). Whether the Oort cloud merges, in its inner region, into the disk-shaped Kuiper belt is not known. How to thank TFD for its existence? Tell a friend about us, add a link to this page, add the site to iGoogle, or visit webmaster's page for free fun content. |
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Some planetary scientists call this proposed assemblage the inner Oort cloud. To resolve the contradiction, theorists in 1981 added another wrinkle to the Oort theory: an inner Oort cloud within the larger sphere, 10,000 to 20,000 AU from the sun, that would act as a reservoir, slowly feeding new comets into the main, outer cloud. |
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