Smithsonian Astrophysical Observatory

Science Updates


Galaxy clusters are groupings of several to thousands of galaxies. Most galaxies are members of a cluster. In our own case, the Milky Way is a member of the "Local Group," a band of about fifty galaxies whose other large member is the Andromeda galaxy about 2.3 million light-years away.


Perhaps the most astonishing and revolutionary discovery in cosmology was that galaxies are moving away from us. Hubble's 1929 paper provides the underpinning of the big bang picture of creation in which the universe is expanding, and has been for 13.8 billion years.

The Smithsonian Astrophysical Observatory (SAO) is a "research institute" of the Smithsonian Institution. It is joined with the Harvard College Observatory (HCO) to form the Harvard-Smithsonian Center for Astrophysics (CfA). Because these research activities share Harvard and Smithsonian staff and resources, the links at this website will take you to information posted on the "CfA" pages.