Large Scale Structure of the Universe

In the mid 1980s, observers concluded that the Local Group of nearby galaxies reside near the edge of the Local Supercluster, a lumpy sheet of galaxies some 100 million years across that has as neighbors the Hydra-Centaurus Supercluster. In 1987 the dimensions of lumpiness continued to grow: it was discovered that the Local Supercluster and its neighbors all belong to a much larger "complex" of superclusters. The strucutre is the largest ever found: it spans about a tenth of the observable universe. It is called the Pisces-Cetus Supercluster Complex. The mapping is that of clusters containing about 1,000 galaxies each.

The mapping is confined to to a cosmic sphere with a radius of one billion light years centered on the Milky Way. Observations of galaxies outside the sphere are incomplete.


"Complexes of Galaxies" populate a sphere 600 Mpc (two billion light-years) across in a map made by R. Brent Tully. The Pisces-Cetus Supercluster Complex is the horizontal structure: three other supersluster complexes-Aquarius, hercules-Corona Borealis and Leo—appear respective at the upper left, upper right and lower left. The empty wedges (purple, barely discernable) are regions that have been obscured by dust in the Milky Way.