Fig12_17 Sloan great wall

Fig12_17 Sloan great wall

Fig. 12.17 . By measuring the recession velocity, or redshift, of galaxies, astronomers have determined their distance and combined it with their location in the sky to obtain the three-dimensional distribution of galaxies. The map shown here is for galaxies within one billion light-years (far left or far right) from the Earth (center). Since galaxies started to form about 12 billion years ago this is a relatively nearby part of the universe. It includes recession velocities of up to 30,0000 km s-1, at a redshift of 0.1. The galaxies are concentrated in long, narrow sheet-like walls encircling large empty places known as voids, about 100 million light-years across. The Sloan Great Wall (left) spans about 1.4 billion light-years. It may be gravitationally unbound, perhaps beginning to fall apart, but this great wall includes superclusters of galaxies that may stay bound together by their mutual gravitational pull. The Sloan Great Wall was discovered using data from the Sloan Digital Sky Survey in 2004. Other superclusters, or clusters of galaxy clusters, are labeled in the diagram, which is from the Two Degree Field galaxy survey. (Courtesy of Willem Schaap, Kapteyn Institute, U. Groningen et al., 2dF Galaxy Redshift Survey).

Copyright 2010, Professor Kenneth R. Lang, Tufts University