What Are Comets
Comets 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. They are sometimes called dirty snowballs or icy mudballs because of this.comets come in a variety of shapes and sizes. Some can be quite large like in 1811, a huge comet appeared in the sky. Its head was a cloud of dust that was said to be larger than the sun; its tail stretched for millions of miles. As of 1995, 878 comets have been cataloged and their orbits at least roughly calculated. But because of gravitational interactions, a number of periodic comets discovered in earlier decades or previous centuries are now lost, since their orbits were never known well enough to know where to look for thier future appearances.
Comets have several distinct parts: the nucleus, coma, hydrogen cloud, dust tail, and ion tail. The nucleus is relatively solid and stable ,mostly ice and gas with a small amount of dust and other solids. The coma is a dense cloud of water, carbon dioxide and other neutral gases sublimed from the nucleus. The hydrogen cloud is huge. It is millions of kilometers in diameter but it's a very sparse envelope of neutral hydrogen. The dust trail of a comet is up to 10 million kilometers long. It is composed of smoke-sized dust particles driven off the nucleus escaping gases . The ion tail is as much as several hundred million kilometers long. It is composed plasma and laced with rays and steamers caused by interactions with the solar wind. A comet tail gets longer as the comet gets brighter. Comets have highly elliptical orbits that bring them very close to the Sun and swing them deeply into space, often beyond the orbit of Pluto. Comets are made up of meteorites. Meteorites are masses of stone or iron that have struck earth from interplanetary space.
Comets are believed to originate in a distant cloud known as the oort cloud. An oort cloud is a grouping...
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