University of Iowa researchers have found a star orbiting a "medium-sized" black hole -- about 1,000 times more massive than the sun -- in the nearby starburst galaxy M82, a development that may help explain how medium-sized black holes form and evolve, according to a paper to be published in the Jan. 5 issue of Science Express, the online version of the journal Science.
Philip Kaaret, associate professor in the UI College of Liberal Arts and Sciences Department of Physics and Astronomy, made the discovery indirectly, by detecting modulations in X-rays produced by the black hole. His associates in the work were assistant professor Cornelia Lang and student Melanie Simet, a senior from Cedar Falls, Iowa.
"We discovered that the X-rays from the black hole get repeatedly brighter and dimmer every 62 days," he said. "This told us that the companion star orbiting around the black hole makes one orbit every 62 days. This, in turn, told us that the companion star has to be a giant star -- a phase in the evolution of a star when it becomes extremely bloated."
Gary Galluzzo | EurekAlert!
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