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 km/s.