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University of Iowa News Release


April 29, 2010

UI researcher, colleagues discover two medium-sized black holes

A University of Iowa researcher and his colleagues have found good evidence for the existence of two medium-sized black holes close to the center of a nearby starburst galaxy, M82, located 12 million light years from Earth.

Because they avoided falling into the galactic center, the black holes may help scientists understand the seeds that give rise to supermassive black holes in other galaxies, including our own Milky Way galaxy.

Philip Kaaret, professor of physics and astronomy in the UI College of Liberal Arts and Sciences, said that one current theory of supermassive black hole formation suggests chain reaction collisions of stars within compact star clusters can create extremely massive stars, which, in turn, collapse to form intermediate-mass black holes. The star clusters migrate to the centers of galaxies, where intermediate-mass black holes merge into supermassive black holes. Clusters that are insufficiently massive or too distant from the galactic center would survive, as would any black holes they contain.

"Finding two medium-sized black holes in one galaxy that's similar to small, star-forming galaxies that predominated when the universe was young suggests that this process may have been important in forming large galaxies like our own Milky Way," Kaaret said.

His colleagues include Hua Feng of Tsinghua University in China and a former UI postdoctoral student, lead author of two papers on the subject recently published in The Astrophysical Journal.

The data was collected using NASA's Chandra X-ray Observatory and ESA's XMM-Newton spacecraft.

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