Smithsonian Astrophysical Observatory

Science Updates


The path of light is bent by mass, an effect predicted by Einstein's theory of gravity, and when a massive galaxy or cluster lies along our line-of-sight to a more distant galaxy its matter will act as a lens to image the light from that object.


Most galaxies lie in clusters containing from a few to thousands of other galaxies. Our Milky Way, for example, belongs to the Local Group cluster of about fifty galaxies whose other large member, the Andromeda galaxy, is about 2.3 million light-years away.

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.