Some details about Galaxies

Galaxies 

                A galaxy is a system of stars, dust and gas physically bound together by gravity. The galaxies are the building blocks of the Universe. The universe includes everything from the smallest sub-atomic particle to the largest galaxies and groups of galaxies. 

          The Milky way is a galaxy consisting of about hundred billion stars. It includes the sun, the earth and rest of our solar system. It is thick in the middle and thin at the edges. In the Milky way the sun is situated at a distance of 27,000 light years away from the centre.

           Astronomers estimate as many galaxies as are stars in the Milky way. They classify the galaxies according to their appearance and shape. There are three main types: spiral galaxies, elliptical galaxies and irregular galaxies. Milky way is a spiral type galaxy.

             Only three galaxies outside the Milky way can be seen from the earth without a telescope. Andromeda is the nearest major galaxy to the earth. Andromeda galaxy is 2x10⁶ light years away from our galaxy. People in the northern hemisphere can see Andromeda galaxy.

           People in the southern hemisphere can also see two galaxies, the large and small Magnellanic clouds, which are about 160000 and 180000 light years away. The three visible galaxies can be seen most easily on clear and dark nights.