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Webmaster: Anees Udyawar
Copyright 1998, 1997 by Geocities Corp.

This site is restrictedly for educational, entertainment and leisure purposes.

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Halley's Comet

By:Anees Udyawar

This is a brief research report I had performed in my English class, and wished to put on the internet that other people may achieve some informations on this extraordinary comet!

Comet's do not follow the rules of heavenly bodies like stars, sun, moon and planets. A comet can appear in the sky without warning, they become brighter and brighter for a while then grow dimmer and dimmer and will finally disappear. Comet coming like that unexpectedly, seemed to be a warning of something unusual. To most people "something unusual" was frightening in the beginning! One way to prove that the sight of a comet was disaster is that people would record the year of an appearance of a comet and then would describe the terrible events and things that took place soon afterwards. Of course, terrible things happen every year, whether comets appear or not. Take for instance a comet was sighted in 11 BC which was then connected with the assassination of Julius Caesar in the very same year. Or when a comet was spotted in 66 AD and four years later in 70 AD Jerusalem fell into Roman hands. Also when the fall of Constantinople to the Turks in 1453 was blamed on a comet that appeared in 1456. Can this be true that comet's are viewed as a heavenly comment on the destruction of mankind? Comets often become scapegoats for historical events around the world, because there is nothing else to take the blame for!

Finally in 1682, and English astronomer, named Edmund Halley observed a bright comet in the sky, and began his attempts to calculate its orbit. It was not an easy task at first, but Halley worked on it for many years. He was soon surprised to notice that the comets sighted in 1066, 1145, 1222, 1301, 1378, 1456, 1531, 1607, and 1682, had traveled across the same portion of the sky, and so he deducted the comets to be Halley's comet. After Halley calculated that it took 75-76 years between each comet sighting, he predicted that the same comet will again appear in 1758, but he never got a chance to see his comet again because he died in 1742! Sighting of comets that are most spectacular are ones with very long orbits that approach the sun only once in many thousand years. These types of comets have few occasions when they come close to our sun. When this happens they only lose some of their particles and survive much longer.

Comets that appear once in a thousand years are called "new comets" because when they do appear it will be the first time they will ever be observed scientifically. A good time to look for a new comet is to look for it at night or in early morning with a powerful telescope. Of course if you do sight a comet you should make sure that the comet has not already been discovered before by somebody else. So how many comets are there? Kepler, when asked this question four centuries ago answered, "As many as there are fish in the sea". Nowadays we see many more comets than people did in Kepler's time, for now we have the telescope, so that a new comet is spotted on the average on two to three weeks. So the next question is, how are comets formed? Well there is not enough evidence for scientists to make a clear assumption.

The general thought among astronomers now that the entire solar system originated about 4,600 billion years ago, from a vast slowly whirling cloud of dust and gas that gradually contracted under the pull of its own gravitation. On the very rim of this cloud was material that did not share in the contracting process. It was too far away from the center to be sufficiently effected by the gravitational pull, and it tended to remain where it was. Turbulence made it coalesce into small icy bodies and so forming comets.

A good idea of how faraway comets might recede came in 1973, when a Czech astronomer, Lubos Kohoutek detected an approaching comet while it was still beyond the orbit of Jupiter. Because it could be seen from so far away, it seemed to be a large comet, and therefore a new comet coming from far out in the depths of space. When the path of the comet was plotted, its orbit turned out to be the most enormous ever calculated for any body in the solar system. It is 102 times as far away from the sun as Halley's comet ever gets. This takes Comet Kohoutek over 200,000 years to go once about its orbit around the sun.

What now concerns people is the possibility of collision with a comet. The chance of collision with ant one comet is virtually zero, but if there are a great many comets, the chance of collision with any one of them, sooner or later is very great. Comets that have short orbits around the sun (short-orbit comets) vaporize quicker than the (long-orbit comets). This is because each time a comet comes close to the sun some of its particle evaporates, because the comet is composed of frozen gas and so becomes dimmer each time it gets close to the sun and will finally vaporize. Comets are only visible when near the sun because the intense solar radiation vaporizes parts of icy nucleus from the comet's coma and tail.

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