Galaxy

Basic concept of galaxy.

GALAXY    : In 1805, Hershel made it clear that the solar system was a part of the much larger system of stars called galagy.Edwin hubble in 1924 first demonstrated existence of galaxies beyond  milky way. He proved that these galaxies are flying away from each other and that the farther they are, the faster they fly.this means that the universe is expanding like a balloon that is being blow up.               A galaxy is a vast system of billions of stars, which also contains a large number of gas clouds ( mainly of hydrogen gas ) and dust, isolated in space from similar systems.There are about 100 billion galaxies in the universe , and each galaxy has on an average 100 billion stars. so,the total number of stars in the universe is ten to the power twenty two stars. The milky way galaxy is the home of the earth and solar system. it is spiral in shape . Milky way galaxy was found five billion years after the big bang. Latest know is the dwarf galaxy. According to the modern thought , universe can be classified into two parts namely-atmosphere and space. Origin of the universe is explained by the big bang theory, is formulated and proposed by belgian astronomer and cosmologist Georges Lemaitre after his becoming acquainted with the findings of the american astronomers Edwin p. Hubble and Harlow shapely on the expanding universe .

BIG BANG THEORY :All the matter in the universe was originally concentrated in one lump called primeral atom.  Big bang was an explosion that occurred 15 billion years ago,leading to the formation of the galaxies of stars and other heavenly bodies.Since then, all the galaxies have been flying away from each other causing expansion  of the universe.