Paragraph on “Comets” complete paragraph for Class 9, Class 10, Class 11 and Class 12

Comets

Comets are visible at night and they look very much like meteors and meteorites but in reality they are different. When we see a comet in the sky we notice that it has a bright head and a glowing tail following it as it shoots across the sky. On a closer examination through a telescope we see a bright head, called the ‘coma’ and a large cloud of glowing dust and gases following it. A cornet in reality has a nucleus comprising of ice and dust and an outer body comprising of dust and gas. It is about a kilometre across in size. Comets have their own paths and orbits around the Sun. As the comet passes close to the Sun the ice is converted into gas because of this heat and the dust is expelled into space. Solar winds released by the Sun blow the tail away from the coma. When a comet approaches the Sun the tail follows it but as it moves away from the Sun, the tail tends to lead it. A comet’s tail can at times be as long as 100 million kilometres. The tail is white in colour because the dust particles reflect the Sun’s light. There have been comets which have had more than one tail, in fact in the year 1744 a bright comet with six tails was observed by astronomers.

Most comets take millions of years to complete an orbit and they go all the way around Pluto, which explains their sudden appearance, since they do not become visible till they are close to the Sun. The Comet ‘West’ was last seen in 1976 and would not appear for a million years. There are however comets which have a fixed appearance, for example the Halley’s comet regularly appears every 76 years and was last seen in 1986. As comets reappear they lose most of their ice and gas as a result of which, comets which could be seen in the daylight, may be visible only at night when they reappear. Astronomers believe that there are as many as one million million comets in space.