The Stars

One Night some years ago , people in middle Atlantic States turned in to a radio program . What they heard was imaginary and meant to be entertaining . Actually , it frightened many of them out of a night's sleep. Some fled in panic from the cities toward Canada . Others  got whatever weapons they could to defend their homes . The cause of this wild panic was a vivid description on the radio program of a imaginary attack on the New Jersey region by men from Mars .

Once Upon A time :-

                                The people of ancient civilization spent a good deal of time wondering about the different objects in the sky . A teacher named Aristarchus of Samos , an island in the Aegean Sea , said that the earth revolves around the sun . Aristarchus lived between 310 and 250 B.C. 

 1) Stars and Suns :

                                                   The astronomer of ancient times knew nothing of the real nature of stars . to him they were simply mysterious ornaments in the sky  dome . The astronomers of today knows that the stars are brilliant fiery suns similar to our own sun but they  very much farther away . If our sun were far enough from us , it would look like a star . On the other hand , if any of the stars were close enough to us , they look like a Suns .

2) Seeing Stars :

                              The darker the surrounding the easier it is to see the stars . The starry sky looks brightest on a night when there is no moon and from a position where no street lights or other artificial light can blur the light of the stars . Stars are in the sky by days as well as by night , but the brilliant light of the sun completly outshines their far fainter light , making the stars quite invisible . 

3) How many Stars ?

                                  While the brilliance of the sky on a clear moonless night shows an infinite number of star-by-star count reveals about 5000 stars actually visible to the naked eyes in the heavens of both the Northern and Southern Hemispheres . only about 2000 of these stars can be seen by an observer at any one time . But with aid of modern times , millions of stars can be seen , while more millions of stars can be seen , while more millions of still fainter stars can be shown by photographic plates that are much more sensitive than the human eyes . 

4) The Telescope :

                                           The telescope is an instrument whose lens or mirror , much larger than the lens of the human eye , can gather together a much greater quantity of light from a star and focus it in one spot , it sees hundreds or thousands of times as much light from the stars as it can see " Naked " or without the telescope . Stars already visible look much brighter -not larger -and  millions of stars that are visible through the telescope . Sensitive  Photographic plates , placed at the focus of the telescope's light and exposed for many hours , show large numbers of stars that the eye , even through the telescope , is unable to preceive . 

The great 36-inch Refracting telescope of the University of California's Lick observatory at Mount Hamilton , California .

    A Telescope that uses lenses to focus straight is called Refracting Telescope or Refractor  . The World's largest refractors are those of the Yerkes Observatory at William Bay in Wisconsin , and the Lick observatory at Mount Hamilton in California .The Yerkes lens is 40 inches in Diameter ; the Lick lens 36 inches in it's diameter .

Yerkes Observatory , Geneva

A telescope that uses a curved mirror  to focus the starlight is called a Reflecting Telescope or Reflector . The word's largest reflectors are the telescopes at the Mount Palomar and Mount Wilson ,both in  California . The Palomar mirror is 200 inches , or almost 17 feet , in diameter  ! The Mount Wilson mirror is 100 inches in diameter .

Mount Wilson Observatory

As from above we can only imagined that the Telescope of above  observatory is How Big it ? For we can imagine as saw the image as it above show .....!!!!!!                          

 5) What Stars are made of :

                                                The Chemical composition of a star  can be determined by the Spectroscope . Stars like the sun , are made of Chemical elements so hot that all of them  are in the form of  glowing gas vapor . The Spectroscope  is an instrument  which analyzes the light given off by incandescent (glowing hot) material so that the scientist can tell which elements they contain .Thus far 66 & 92 natural elements have been identified in our sun ,and the other stars appear to be made of the same elements .

6) How  large is a Star  ?

                                         There is a tremendous  range in the sizes of stars , known as Dwarfs ,  have diameters of about 10,000 miles , making them only a little larger than the earth .The Largest star known as Giants , have  diameters upto 2,000,000,000 ( 2 billions ) miles !  . Our sun ,an average -sized 

Star , has a diameter of 864,000 miles a distance almost equal to four trips from the earth to the moon .

Antares and Betelgeuse ,two of the bright stars of our Whole Sky ,are classed among the giants , with the diameters hundreds of times as a Large as the sun's .

Our Daytime Star :

                                  We may guessed by now that just as the earth is not only planet in the sky , so our sun is not the only sun in the space . Actually each star is a sun , & our sun is a medium - sized star as star go . Even so , our sun is more than a hundred times  larger in diameter than the earth . The sun's diameter is approximately 864,000 miles . it would require more than a million earths to equal the volume of he sun .

                                 The earth's distance from the sun varies from 91,500,000 miles in January to 94,500,000 miles in July  but the figure usually mentioned is the average distance of  93,000,000 miles .

                             Until the 17th century , the sun was regarded by everyone as a uniform , fiery ball , but 1610 Galileo discovered spots on it's surface .Further observations revealed that these sunspots were moving across the sun's surface at the different speeds . Later , scientist discovered that the sun is gaseous and not solid  and that the sun rotates or spin's . Although the sun is a globe of glowing gas , it is known as weigh 1.4 times as much as an equal volume of water .No one could come within 50,000,000 miles of it without burning up .The surface temperature  of the sun is about 10,000 ℉ . and its internal temperature is estimated at about 68,000,000 ℉ . Only a tiny fraction of the heat radiated  from the sun is received by each of the planets . The Earth gets about one Billionth part of the sun's Radiation .

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 .