A supercluster is a cluster of clusters of galaxies. Superclusters range in size from 100 million to at least 300 million light-years across and typically contain tens of thousands of galaxies. They are usually embedded in large sheets and walls of galaxies surrounding immense voids in which very few galaxies exist. Superclusters are believed to have formed in the early universe when matter clumped together under the influence of gravity. Our galaxy lies within the Local Supercluster. The largest known supercluster is the Shapley Concentration. According to one recent survey, there are 130 superclusters out to a distance corresponding to a redshift of z = 0.1 (about 300 Mpc/h).

 

Local Supercluster

The Local Supercluster is the supercluster to which our own Local Group of galaxies belongs (Figure 2). By supercluster standards it is of very modest size with only one rich cluster of galaxies (containing many galaxies in a relatively compact region), the Virgo Cluster, at its center; the Local Group, which belongs to the Canes Venatici cloud of galaxies, lies in the outskirts. The Local Supercluster appears to be made of two major structures: a flattened disk, which has a thickness of about 5 million light-years and contains about 60% of the bright galaxies, and a roughly spherical halo, which contains the remaining 40% of the bright galaxies in a small number of clouds.