Great Wall (astronomy)

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This article is about the CfA2 Great Wall. For the Sloan Great Wall, see Sloan Great Wall. For other uses see Great Wall (disambiguation).

The Great Wall, sometimes more specifically referred to as the CfA2 Great Wall, is the second largest known super-structure in the Universe. 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 only 15 million light-years thick. It was discovered in 1989 by Margaret Geller and John Huchra based on redshift survey data from the CfA Redshift Survey^[1].

It is not known how much further 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 obscures astronomers' view and have so far made it impossible to determine if the wall ends or continues on further than they can currently observe.

It is hypothesized that such structures as the Great Wall form along and follow web-like strings of dark matter. It is thought that this dark matter dictates the structure of the Universe on the grandest of scales. Dark matter gravitationally attracts normal matter, and it is this normal matter that astronomers see forming long thin walls of Super-Galactic clusters.

The largest known cosmic structure is the Sloan Great Wall, discovered in 2003 in data from the Sloan Digital Sky Survey; it is about a billion light-years away, and about 1.4 billion light-years in length.