Q&A: Black Holes

Q:
I would like to know if Sagittarius A* is exactly in the center of the Milky Way. If not, then where is it? I heard that it is not in the center because it balances the galaxy's density. Is this correct?

A:
Astronomers believe there is a black hole in the center of our galaxy. We've carefully observed the motion of stars orbiting very close to the central mass of our galaxy, and from their velocity and position we can conclude that there is a dark massive body in the center of the galaxy, with a mass approximately 3 million times that of the Sun. The rest of the galaxy revolves around the central mass very calmly.

Our central black hole is called Sagittarius A* (pronounced as "sagittarius a star") and we have a beautiful Chandra X-ray image of it at:
http://chandra.harvard.edu/photo/2003/0203long/

There are many links at the bottom of that page with more information on both black holes and the center of our galaxy.