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The Question

(Submitted November 10, 1996)

I am an Italian girl and I'm eleven years old. I should like to know the principle sources known of the X-rays and Gamma-rays in the Universe. Thank you very much .

The Answer

Thank you for you interest. It is impressive that someone so young is interested in these topics. There are many types of sources that produce X-rays, gamma-rays or both. Two types of objects, "active galactic nuclei" (which include quasars), and "X-ray binaries" produce X-rays and to a lesser extent, gamma-rays. Active galactic nuclei are most likely powered by supermassive black holes (as massive as millions to billions of suns). Some X-ray binaries may also contain black holes. Supernova explosions also produce a lot of X- and gamma radiation. There is hot gas in some galaxies, including our Milky Way, that produces X-rays. Stars, including our Sun, produce X-rays, particularly in their coronae. There is also a mysterious phenomenon called "gamma-ray bursts" which are now being detected daily by the Compton Gamma-Ray Observatory. Scientists are not sure yet what these are, but they are very energetic. For more information on these topics, try looking at the Learning Center Web pages.

Have fun,
Andy Ptak and the Ask an Astrophysicist team

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