Smithsonian Astrophysical Observatory

Science Updates


Galaxies actively engaged in making stars produce many hot massive stars that emit copious amounts of uv radiation. The neutral hydrogen gas in these galaxies (or in the intervening intergalactic medium) absorbs nearly all the uv light that is shorter than 912 Angstroms, the characteristic wavelength of the hydrogen transition.


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