вторник, 21 января 2020 г.

Comets Essay -- Astronomy Essays Space Outer

Comets   Ã‚  Ã‚  Ã‚  Ã‚  Have you ever looked up in the sky and seen a little ball creeping by? If so, did you wonder what it was? That little ball is called a comet. Comets are small, fragile, and irregularly shaped. Most are composed of frozen gas. However, some are composed of frozen gas and non-volatile grains. They usually follow very strict paths around the sun. Comets become most visible when they cross the sun. This also applies to people who view comets with telescopes. When a comet gets near the sun it becomes very visible because the sun's radiation starts to sublime its volatile gases, which, in turn, blow away small bits of the little solid material the comet has.   Ã‚  Ã‚  Ã‚  Ã‚  Another feature of a comet is a long tail. This is caused by materials breaking off and expanding. They expand into an enormous escaping atmosphere called the coma. This becomes at least the size of our planet. With the comet going so fast, these materials are forced behind the comet, forming a long tail of dust and gas.   Ã‚  Ã‚  Ã‚  Ã‚  Comets are cold bodies. We see them only because the gases they are composed of glow in the sunlight. All comets are regular family members of the solar system family. They are bound by gravity to a strict path around the solar system. Scientists believe that all comets were formed of material, originally in the outer part of the solar system, which did not become incorporated into planets. This material is from when the planets just started forming. This makes comets an extremely interesting topic to scientists who are studying the history of the solar system.   Ã‚  Ã‚  Ã‚  Ã‚  In comparison to planets, comets are very small. They can be anywhere from 750 meters (or less) to 20 kilometers in diameter. However, lately, scientists have been finding proof that there are comets 300 kilometers in diameter or greater.   Ã‚  Ã‚  Ã‚  Ã‚  Comets are still compared to the planets, though. Planets usually follow the shape of a sphere. Most planets are fat at the equator. Comets come in all different shapes and sizes. Most evidence that science has revealed says that comets are extremely fragile. A comet is so poorly structured that it is like a loose snowball--it can be pulled apart with one's own bare hands.   Ã‚  Ã‚  Ã‚  Ã‚  Comets have very awkward rotation periods. They are very oblong. When comets reach their aphelion they are usually near Jupiter or even sometimes Ne... ... is expected to reach its closed point to the sun. At this time it will also be most visible because the sun reflects off the tail of the comet.   Ã‚  Ã‚  Ã‚  Ã‚  It will come .914 astronomical units from the sun. This is not all that close to the sun considering the fact that some comets have run into the sun and others have skimmed the surface of it.   Ã‚  Ã‚  Ã‚  Ã‚  Although the comet will be closest to the sun on April 1, it will be closest to the earth on March 23, 1997. Some people have been saying that the comet will hit earth and cause human extinction, just like the dinosaurs. The fact is, however, THE COMET WILL NOT HIT EARTH. The closest it will come is 120 million miles away from the earth.   Ã‚  Ã‚  Ã‚  Ã‚  Some people are saying that the comet is going to Be huge, and others say it will be small. We will never know though because we can not see the nucleus of a comet. The part of the comet we see is the tail. The tail of a comet can be over 10,000 kilometers long.   Ã‚  Ã‚  Ã‚  Ã‚  In all, comets, the history of comets, and comets waiting to be discovered is very interesting. I think that one day we will get to see the nucleus of a comet, and be able to watch comets form in the Oort Cloud.

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