Smithsonian Astrophysical Observatory

Science Updates


Our Milky Way galaxy is a barred spiral galaxy, a flattened disk of stars, gas and dust about 100,000 light-years in diameter containing several hundred billion stars.


The nuclei of most galaxies contain a massive black hole. In our Milky Way, for example, the nuclear black hole contains about four million solar masses of material, and in other galaxies the black holes are estimated to have masses of hundreds of millions of suns, or even more.

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.