CfA Redshift Survey

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CfA Redshift Survey

The CfA Redshift Survey was the first major project to map the universe’s large-scale structure. It was run by the Center for Astrophysics (CfA) and began in 1977 at the Smithsonian Astrophysical Observatory in Cambridge, Massachusetts.

What redshift means: When galaxies move away from us, their light shifts toward longer wavelengths. This redshift lets astronomers measure how fast a galaxy is receding and, with Hubble’s law, how far away it is. By collecting redshifts for many galaxies, scientists can build a 3D map of the nearby universe.

The first survey (CfA1): The initial data collection was completed by 1982, measuring redshifts of brighter galaxies to create a 3D map of that region.

The second survey (CfA2): Begun in 1985 by John Huchra and Margaret Geller, it measured redshifts for about 18,000 bright galaxies in the Northern sky by 1995. The results showed that galaxies are not evenly spread; they cluster in surfaces around large empty voids. The survey also led to the discovery of the Great Wall, a gigantic supercluster of galaxies surrounded by voids, bigger than scientists had expected from simple gravitational collapse in the early universe.

Impact and meaning: The CfA Redshift Survey showed that the universe has a “cosmic web” of clusters, voids, and superclusters. It supported ideas that the large-scale structure grew from tiny fluctuations in the early universe during cosmic inflation.