Most elliptical galaxies are composed of older, low-mass stars, with a sparse interstellar medium and minimal (or no)star formation activity. They tend to be surrounded by large numbers of globular clusters. Elliptical galaxies are believed to make up approximately 10–15% of galaxies in the Virgo Supercluster, but are not the dominant type of galaxy in the universe overall. They are usually found close to the centers of galaxy clusters.