The Virgo Supercluster
The Virgo Supercluster (Virgo SC) or the Local Supercluster (LS) is a mass concentration of galaxies that contains the Virgo Cluster in addition to the Local Group, which in turn contains the Milky Way and Andromeda Galaxies. At least 2,000 galaxy groups and clusters are located within its diameter of 110 million light-years, and 65 million light-years away from Earth. It is one of millions of superclusters in the observable universe. A 2014 study indicates that the Virgo Supercluster is only a lobe of a greater supercluster, Laniakea, which is centered on the Great Attractor.
Beginning with the first large sample of nebulae published by William and John Herschel in 1863, it was known that there is a marked excess of nebular fields in the constellation Virgo (near the north galactic pole). In the 1950s, French–American astronomer Gérard Henri de Vaucouleurs was the first to argue that this excess represented a large-scale galaxy-like structure, coining the term “Local Supergalaxy” in 1953 which he changed to “Local Supercluster” in 1958. Debate went on during the 1960s and 1970s as to whether the Local Supercluster (LS) was actually a structure or a chance alignment of galaxies. The issue was resolved with the large redshift surveys of the late 1970s and early 1980s, which convincingly showed the flattened concentration of galaxies along the supergalactic plane.
In a comprehensive 1982 paper, R. Brent Tully presented the conclusions of his research concerning the basic structure of the LS. It consists of two components: an appreciably flattened disk containing two-thirds of the supercluster’s luminous galaxies, and a roughly spherical halo containing the remaining one-third. The LS represents a typical poor (that is, lacking a high density core) supercluster of rather small size. It has one rich galaxy cluster in the center, surrounded by filaments of galaxies and poor groups. The Local Group is located on the outskirts of the LS in a small filament extending from the Fornax Cluster to the Virgo Cluster. The Virgo Supercluster’s volume is very approximately 7000 times that of the Local Group or 100 billion times that of the Milky Way.