Cone diagram for 2500 galaxies between declinations 26.5 and 44.5°. The Great Wall runs across the survey. (From: M.J. Geller and J.P. Huchra).
The Great Wall is a sheet of galaxies measuring some 200 million by 600 million light-years in area but with a thickness of only about 20 million light-years. One of the largest known structures in the universe, it lies 300 to 400 million light-years from the Milky Way and appears to connect the Coma and Hercules superclusters. It was discovered in 1988–89 by Margarite Geller and John Huchra at the Center for Astrophysics while investigating data from a survey of 1,060 galaxies. The Great Wall stretches from R.A. 8h to 17h and from Dec. +26° to +32°, and influences the motions of galaxies with recession velocities (due to the expansion of the universe) of 7,000 to 10,000 kilometers per second.