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 c...