![]() ![]() Comet Halley is the source of the Orionid shower in October. Some occur with great regularity: the Perseid meteor shower occurs every year between August 9 and 13 when the Earth passes thru the orbit of Comet Swift-Tuttle. Meteor shower sometimes occur when the Earth passes thru the orbit of a comet. with Jupiter).īy far the most famous comet is Comet Halley but SL 9 was a "big hit" for a week in the summer of 1994. ![]() (Perhaps half of the near-Earth asteroids may be "dead" comets.) A comet whose orbit takes it near the Sun is also likely to either impact one of the planets or the Sun or to be ejected out of the solar system by a close encounter (esp. Only the short- and intermediate-period comets (like Comet Halley), stay within the orbit of Pluto for a significant fraction of their orbits.Īfter 500 or so passes near the Sun off most of a comet's ice and gas is lost leaving a rocky object very much like an asteroid in appearance. Most comets have highly eccentric orbits which take them far beyond the orbit of Pluto these are seen once and then disappear for millennia. ion tail: as much as several hundred million km long composed of plasma and laced with rays and streamers caused by interactions with the solar wind.Ĭomets are invisible except when they are near the Sun.dust tail: up to 10 million km long composed of smoke-sized dust particles driven off the nucleus by escaping gases this is the most prominent part of a comet to the unaided eye.hydrogen cloud: huge (millions of km in diameter) but very sparse envelope of neutral hydrogen.coma: dense cloud of water, carbon dioxide and other neutral gases sublimed from the nucleus.nucleus: relatively solid and stable, mostly ice and gas with a small amount of dust and other solids.When they are near the Sun and active, comets have several distinct parts: This makes them very interesting as samples of the early history of the solar system. They are a mixture of ices (both water and frozen gases) and dust that for some reason didn't get incorporated into planets when the solar system was formed. Of these 184 are periodic comets (orbital periods less than 200 years) some of the remainder are no doubt periodic as well, but their orbits have not been determined with sufficient accuracy to tell for sure.Ĭomets are sometimes called dirty snowballs or "icy mudballs". As of 1995, 878 comets have been cataloged and their orbits at least roughly calculated. ![]()
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