Rogue black holes may roam the Milky Way

April 29, 2009 |

It sounds like the plot of a sci-fi movie: rogue black holes roaming our galaxy, threatening to swallow anything that gets too close. In fact, new calculations by Ryan O’Leary and Avi Loeb (Harvard-Smithsonian Center for Astrophysics) suggest that hundreds of massive black holes, left over from the galaxy-building days of the early universe, may wander the Milky Way.

Good news, however: Earth is safe. The closest rogue black hole should reside thousands of light-years away. Astronomers are eager to locate them, though, for the clues they will provide to the formation of the Milky Way.

“These black holes are relics of the Milky Way’s past,” said Loeb. “You could say that we are archaeologists studying those relics to learn about our galaxy’s history and the formation history of black holes in the early universe.”



Hundreds of rogue black holes should be traveling the Milky Way’s outskirts, each containing the mass of 1,000 to 100,000 suns. They would be difficult to spot on their own because a black hole is visible only when it is swallowing, or accreting, matter.



“The surrounding star cluster acts much like a lighthouse that pinpoints a dangerous reef,” explained O’Leary. “Without the shining stars to guide our way, the black holes would be all but impossible to find.”



“Until now, astronomers were not searching for such a population of highly compact star clusters in the Milky Way’s halo,” said Loeb. “Now that we know what to expect, we can examine existing sky surveys for this new class of objects.”

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