# CfA2 Great Wall

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The Great Wall includes clusters Hercules, Coma and Leo on the right of this view of the local universe.

The Great Wall (also called Coma Wall), sometimes specifically referred to as the CfA2 Great Wall, is one of the largest known superstructures in the Universe, (the largest being the Hercules-Corona Borealis Great Wall). It is a filament of galaxies approximately 200 million light-years away and has dimensions which measure over 500 million light-years long, 300 million light-years wide and 16 million light-years thick, and includes the Hercules Supercluster, the Coma Supercluster and the Leo Cluster.[1]

It was discovered in 1989 by Margaret Geller and John Huchra based on redshift survey data from the CfA Redshift Survey.[2]

It is not known how much farther the wall extends due to the plane of the Milky Way galaxy in which Earth is located. The gas and dust from the Milky Way (known as the Zone of Avoidance) obscure the view of astronomers and have so far made it impossible to determine if the wall ends or continues on further than they can currently observe. The volume of the wall is estimated to be approximately $2.0318173 \times 10^{45}$ km³[citation needed].

In the standard model of the evolution of the universe, such structures as the Great Wall form along and follow web-like strings of dark matter.[3] It is thought that this dark matter dictates the structure of the Universe on the grandest of scales. Dark matter gravitationally attracts baryonic matter, and it is this "normal" matter that astronomers see forming long, thin walls of super-galactic clusters.