World Of Galaxies
Nearly all the stars in the universe belong to one of the gigantic groups of stars called Galaxies. And our sun is just one of the hundred billion stars in our galaxy, the Milky Way.
Galaxies are vast regions of space consisting of planets, stars, clouds of gas and dust, and plenty of empty space. There are an estimated hundred billion galaxies in the visible universe. Galaxies may be of different shapes – Spherical , Elliptical or irregular. Only three galaxies are visible in the sky without the telescope. Most pictures and knowledge of other galaxies came from the Hubble Space Telescope.
Galaxies are usually not isolated in space, but are often members of other groups which in turn form large galaxy clusters. Some of the galaxies we know are the Milky Way, Andromeda and the Magellanic cloud. Our nearest galactic neighbor is 2 million light years away (One light year = distance traveled by light in one earth year)
The process of formation of galaxies is still unclear and under debate. But after the “Big Bang”, the whole universe consisted of radiation and sub-atomic particles, and so either the small particles gradually formed stars, planets,etc or the Universe was a huge clump and later broke up.
Galaxies regularly crash into one another, but quite safely owing to their massive size.
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