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Sunday 8 January 2012

Constellations

" What Are Constellations ? "


Image of Constellation
Constellations are groups of stars visible within a particular area of the night sky.Some were named after animals,mythological characters and scientific instruments.Constellations can be viewed after sunset,and before sunrise.Also,as the Earth turns,you can see different constellations at different times of year.



Some of the most famous constellations are 'Andromeda' and 'Orion' the hunter.
The star groups that make up the constellations came from the imaginations of people like sailors,astronomers,and farmers over many thousands of years.So,why did ancient civilizations look to find patterns among the stars ? The answer is simple.These patterns helped them locate the stars,and their position in the sky.On a clear night,you can see about 1500 stars !

The Great Bear is one of the most prominent constellations in the Northern sky.Actually,it does not look like a bear at all,except for its tail.In North America,it is also called The Big Dipper.If you want to see it,go out at night and face North.Look carefully for a pattern of seven stars.If it is autumn,the stars will look like a saucepan with a bent handle.In spring,it will appear as an upside down saucepan,and at other times,a tilted one.However,it should be a very clear night.Otherwise,you will not be able to see The Great Bear.

" How Many Constellations in the Universe ? "


There are 88 official constellations.This number was established by the International Astronomical Union in 1928.Today,this same organization is in charge of naming celestial bodies.It is the only organization recognized by scientists for this purpose.

" Difference Between Constellation And Galaxy "


Constellations are patterns of stars that we see in the sky,like Leo,Orion,Taurus,and others.A galaxy on the other hand,is a system of stars,dust and gas held together by gravity.There are billions of galaxies in the universe,and the galaxy in which we live is called the Milky Way.

" How Galaxies Developed "


Scientists know that stars form out of gas.They beleive that the Universe itself was once all gas,and that clumps of gas joined together to form young galaxies or protogalaxies.The protogalaxies developed in different ways.Some had huge clumps of gas at the center,which formed massive explosions.many massive explosions forced forced the left over gas out of the galaxy,so that only stars formed from the gas,remained.Protogalaxies that developed in this manner become elliptical galaxies.

Sometimes,a protogalaxy will contain only small clumps of gas.Most of the gas is retained along with the stars that have formed,and the galaxy becomes a spiral galaxy.
Irregular galaxies are probably protogalaxies in which explosions are still happening.sometimes,smaller galaxies move towards each other and merge into bigger galaxies.Our Milky Way galaxy came together in this way.

Watch Special Video on Stars and Constellations

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