supercluster

A large group of neighboring clusters of galaxies, along with isolated galaxies scattered between them, the entire collection ranging in size from roughly 10 million to 1 billion light-years in diameter. The distribution of clusters is often close to that of a flattened sphere or disk. The Milky Way belongs to a galactic cluster known as the Local Group, which in turn is a member, along with about a hundred other such clusters, of the Virgo or Local Supercluster. There is some question as to whether gravity holds superclusters together and whether any larger structures exist within which superclusters are organized.