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The Question

(Submitted October 28, 1996)

I am an undergraduate in Astrophysics at the University of Calgary. I am doing a small research project on the evidence for and against a black hole at the center of the milky way. I found your email address on the StarChild page dealing with this topic. I was wondering if you had any suggestions of articles or books discussing this subject. Thank you for your time.

The Answer

It is generally believed that a black hole does exist at the center of the Milky Way galaxy. The latest value we have seen is that it has a mass of about 2,000,000 that of the Sun. In fact, it is believed that this may be common for most galaxies. Observational evidence supports these ideas more and more. However, you must keep in mind that due to the large absorption and source confusion when trying to look into the center of a galaxy, it is very, very hard to see what's there! So we have to be clever about the observations we make and the interpretations of these observations. This is one reason that X-rays and gamma-rays are powerful probes in trying to answer such questions; they are much more likely to "get out" of the central region of the galaxy than other wavelengths.

Some references you may find useful (and which give many more references) are:

  • Sky and Telescope, June 1996, p.28.
  • "ASCA View of Our Galactic Center: Remains of Past Activities in X-Rays?" Publications of the Astronomical Society of Japan, v.48, p.249-255.
A more general Milky Way reference is Blitz, Binney, Lo, Bally & Ho 1993, Nature 361, 417.

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