Columbia University astrophysicists just discovered a dozen black holes held captive in the center of our galaxy by a supermassive black hole known as Sagittarius A. A black hole is a dying star that collapses inward from its own weight. Its strong gravitational pull will not allow even light to escape.
For more than two decades astronomers have believed that thousands of smaller black holes surround supermassive black holes at the centers of large galaxies, but they could not find evidence of them.
Because black holes don’t emit any light, astronomers can’t observe them. In the past scientists have searched for the elusive celestial bodies by looking for the bright bursts of X-rays produced when a black hole and a star begin to orbit each other. But even around Sagittarius A, the mergers take place so far from Earth that bursts of X-ray bright enough to observe occur only about once every 100 to 1,000 years, Charles Hailey, the lead researcher said in a statement.
In the study, published in Nature, the researchers for the first time looked for the weaker, but steadier, X-rays emitted after the initial bonding between a star and a black hole. The new method paid off, and the scientists found 12 binary black holes within three light years of Sagittarius A. Extrapolating from their observations, the scientists believe 300 to 500 black hole binaries and about 10,000 isolated black holes exist in the center of the Milky Way.
The discovery will help astronomers study the interactions between large and smaller black holes, which should help them better understand how large objects in the universe interact, the researchers said. —J.B.