Galaxy cluster, artwork. Galaxies consist of large numbers of stars gravitationally bound together to orbit a common centre. Galaxies themselves are not distributed evenly throughout the universe. They are found in clusters that are also bound together by the force of gravity. This large galaxy cluster contains thousands of galaxies of various shapes and sizes from large spiral galaxies to elliptical galaxies. Elliptical galaxies are the most common type shown and a large elliptical galaxy dominates the centre of the cluster. The scale of this image covers many millions of light years.