A galaxy is a huge assembly of stars, dust and gases, mutually held together by gravitational force . Millions of stars are present in the galaxy and the diameter of galaxy ranges from 1000 light years to one million light years. Our universe contains many galaxies and each galaxy has about billions of stars.
Some of the stars in the galaxy stay in a group called constellation such group of stars staying in certain patterns can be seen clearly in clear moonless night. As looking from the earth, the group of stars resemble with some animals, a group of people, some object, etc . On the basis of what they resemble to,they are given different names. About 88 constellation are known sufor and 12 of them are considered as zodiac. E.g. Ursa major, Scorpio, Orion, etc.
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