It contains over 2500 galaxies, including the giant elliptical galaxy M87. The Virgo cluster is approximately 17 Mpc away. In between the galaxies, there is a significant amount of intergalactic gas, which has been stripped from the galaxies in the cluster. Near the center of a rich cluster, there is usually a giant elliptical galaxy which has been swollen to immense proportions by galactic cannibalism. Clusters are joined into superclusters, which are separated by huge voids.
Clusters of galaxies are themselves clustered.
Superclusters , or clusters of clusters of galaxies, are the largest structures known. It is possible to map the distribution of galaxies in space out to distances of hundreds of Mpc. Draw a map of the galaxy positions in space For a map of the large scale structure of the universe, click here . Superclusters are not spherical, but form flattened walls or elongated filaments. The voids are as much as 100 Mpc across, and contain very few galaxies, in striking contrast to the galaxy-rich superclusters.