UCLA astronomers have presented the first evidence that tens of thousands of black holes are orbiting the monstrous black hole at the center of the Milky Way, 26,000 light years away.

Michael Muno, a UCLA postdoctoral Hubble Fellow, has studied the inner 75 light-years of the Milky Way, searching for bright, highly variable X-ray sources likely to be accreting black holes and neutron stars, using NASA's Chandra X-ray Observatory. Muno found that these "transient" X-ray sources were highly concentrated within three light-years of the Galactic center, and that the one closest to the center, only three-tenths of a light year away, was very likely to be a black hole.

The best explanation for this high concentration of X-ray binaries is that a few of the black holes, which UCLA astronomy professor Mark Morris predicted in 1993 should be there, have captured other stars, and are slowly devouring them. Morris proposed a theory that a process called dynamical friction would cause stellar black holes to sink toward the center of the galaxy. Andrea Ghez, a UCLA professor of physics and astronomy, is a co-author on Muno's research, as is Morris.

NASA funded the research.

Muno presented the findings on January 10 at the national conference of the American Astronomical Society, which met in San Diego.