This is the first big discovery made by the X-ray space observatory which was specifically designed to hunt black holes.
Scientists said the discoveries were made "serendipitously" as astronomers were reviewing images from NASA's NuSTAR.
"We were looking at known targets and spotted the black holes in the background of the images," David Alexander, a professor with Durham University's physics department, said in a statement.
The 10 black holes are just the beginning of the hundreds NASA expects to find. According to scientists, once every super-massive black hole is cataloged they'll be able to have a better understanding of the population.
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