WHAT IS A
GALAXIES ?
A galaxies is a collection of stars as well as dust and gas clouds. Although all these are several light years away, they are bound together by the force of gravitational attraction. A galaxy is a kind of a ‘star system’. Our home galaxy ,the milky way, has a diameter of about 120,000 light years. It contains several hundred billion stars, and there are billions of such galaxies. They often occur in groups, called galaxy clusters. The cluster to which the milky way belongs is called the ‘Local group’.
WHAT DO GALAXIES LOOK LIKE ?
In most of the galaxies, the stars
are not uniformly distributed, but instead are arranged in certain patterns.
The most frequent ones are spiral galaxies. The center of such galaxies is
thick with several old, red shining stars. A flat disc stretches all around
this center in which the individual arms of the spiral are present. It has a
thickness of just about 100 light years, which is very thin as compared to the size
of a galaxy. The spiral arms contain a lot of young bright blue stars. If a
spiral galaxy has only two arms, it is called barred spiral galaxy. Other types of galaxies are the egg-shaped 'elliptical galaxies' and the 'irregular' galaxies, which are completely disordered.
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