Comet , Meteor & Meterorites

As we look up at the sky on starry night . The heavens appear to form a gigantic dome that hangs over the Earth and is lit up in many places by thousands of points light of varying brightness . Most of these light sparkle and twinkle as through constantly being turned off & on again , but a very few shine with a steadier light than the rest . The light are spread unheavenly through the sky ,& in one large section the whole sky glows white as through sprinkled with" Star Dust " .

  Comets - The Hairy Stars

To the ancients perhaps the most mysterious and dreaded of all the heavenly bodies were the COMETS . Even today many people Speak of comets with awe and fear , although most people have never seen a Comet . As with the stars and the Planets, there are large comets and dim ones ,distant comets and near ones . Most comets can be seen only through the Telescope . A comet visible to the naked eye is even rarer .

                       

As from the ancients , the planets were wandering stars , and comets were hairy stars . Comets are great bright Object in the sky . As they come close to the sun , they grow long tails that may cover several hundred million miles of space . As they swing around the sun , these tails swing ahead of the comet and becomes beareds . (As shown in above figures)

A comet has 3 parts .In addition to the tail , it has ' head ' which may be as much as 10,000 miles across . Around the head is a crown of light which may be several thousand miles from one side to the other . But as comets move away from the sun they become much smalle and fainter . The tails of Comet stretch millions of miles across the sky . The great Comet Of 1843 was said tohave a tail 2000,000,000 miles long .The tail is a glowing mass of gas but it is estimated that if al the material in the tail of a comet could be condesed and gather together , it would fit into an ordinary suitcase . At any rate , the earth has passed through the tails of comets many times without the slightest effect . 

The impact of the head of a comet has another story . Many scientists believe that the crater in Arizona may have been caused by impact of a comet's head . It is likely that head  or nucleus of a comet consists of meteoric material . It is probly not Solid mass , but ma Consist of separate pieces something like a load of buck - shot . In any event , it does not disappear like a tail . The halo light makes it possible for astronomers to track comets as they approach and retreat from the sun . There is many comets seen as from 18th century . The Donati Comet of 1858 , Brook's Comet of 1893 ,Morehouse of 1908 & Cunningham's of 1940  are a few that have been named for their Discovers . 

The most Famous of the comets is Halley's Comet .It was named after the Astronomer Royal of England , Edmund Hally . It's first appearance was noted as early as 240 B.C. Halley in 1682 Calculated its path and predicted its return in 1758 . It came again in 1834 & in1910 . Add 76 years to 1910 and look for it's return in 1986  . Halley was the first astronomer to recognize that comets are members of the Solar System that revolve in orbits around the sun & return to view at the regular intervals . The orbits of the Comets are very large and very Eccentric ; that is , they are off centre , coming much Closer to the sun at one end than at the other .   

 When comets come near the sun they are us & we can see them . Then they go off into the far reaches of the solar system & are out of sight for many years , the number of years depending on the sizes of their orbits .The narrow head of a comet , appaently composed of billions of small bits of rock &dust ,shines brightly by the reflection of sunlight . 

 

The Meteors

Most of us have seen Meteors . We can usually call them "Shooting Star" . Meteors are pieces of stony or metalic rock , most of them as small as sand grains , though some are as large as gigantic boulders . Billions and billions of meteor are widely scattered throught the space of the solar system , some travelling alone and others revolving around the sun in great meteor swarms that include billions of particles . Meteors travel at speeds , and when they approch close enough to the earth , they are pulled toward the earth by Gravitation . Their brilliant streaks of light , rarely lasting more than a second , usually develop only after they come within about 60 miles of earth's surface , and are the result of the intense heat produced by friction with the atmosphere . Meteors whose light is unusually large and bright ae called Fireballs .

If we journey to meteor crater in Arizona , we will see what happen When a large meteor becomes a Meteorite . We will see a crator 3 quarters of miles in diameter with walls 600 feet high . It looks like one craters on the moon . Nearby are many fragments of IRON meteorites. The main mass of the meteorite has never been recovered  . All around , the the limestone rock of the region is powdered as if struck by a Colossal Hammer  .

 

 Small meteors burn up completly in the upper air ; larger ones may land on the earth , where they are called Meteorites . It is estimated that millions of meteor enter the earth atmosphere every hour , but very few reach the surface . The Field Museum in Chicago and the Hayden Planetarium in New York city have execellent collection of the Meteories which show painly how this " visitors from Outer space " different from the earth's own rocks . The largest meteorites weigh many toned .

A few places on earth  gaint Meteorites appear to have crashed into the ground with the enough force to explode deep Craters . The world's largest known crater of this type is Meteor Crater in Arizona . It is almost a mile in diameter & about 600 feet deep . A larger Crater , has been discoverd in the far Northern wilderness of canada , but its Meteoric origin has yet to be proved . Another is in Northen Quebec in Canada . A third is known to be in the forests of Siberia in Russia . 

Crater Of Arizona

Crater on Quebec

Meteor Showers  occure when the earth crosses the orbit of a meteor Swarm . Large mumbers of meteors are seen on such nighs , the "showers" usually being named after the constellation in the sky from whose direction they seem to come . 3 of the best - known Meteor Showers are the Pereseids , which occure every year about August 12 ; the Orionids , which occure about 20 October ; the Geminids , about December 10 . Some of Meteor swarms are believed to have formed when comets that passed near the earth broke up or lost some of the material From their Heads .