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| Galaxy and Stars |
It is said that a very powerful explosion took place billions of years ago which resulted in the formation of the galaxies. Galaxies contain dust, gas and thousands of millions of stars. These galaxies are gradually moving away from each other since the Universe is constantly expanding.
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On a clear night we can see thousands of stars in the skies. Most of the stars we see belong to our galaxy. Some of the tiny dots are in fact for bigger than the Sun but we barely see them because of the distance. Astronomers use powerful telescopes to look into the universe. Some of the galaxies they see are xlise to 100 million light years away. It is because of this that what they see today is fact the light which left that galaxy billions of years ago.
Astronomers are constantly discovering more and more new galaxies each containing thousands of millions of new stars. Galaxies can be classified into three types – irregular, spiral elliptical. The Milky way is a spiral galaxy and our Sun, a medium sized star, with its family of nine planets is located in it. The galaxy is so big that the Sun is only one of the 100 billion stars it has. The milky way has a diameter of about 1,00,000 light years and the Sun is located about 30,000 light years from its center. It travels at a speed of 250 km per second and takes about 225 million years to complete one revolution around the milky way.
Scientists have also discovered Black Holes in the universe obscovered black Holes in the universe observers have seen that whatever goes into the black hole is never seen that whatever goes into the black hole is never seen again.
Besides the observation work carried out by the astronomers in the recent decades unmanned spacecraft and probes have been sent out into space. These spacecraft have sent back invaluable information, to the scientists on earth, about planets like Mars, Jupiter, Neptune and Uranus.
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