Hundreds of "Rogue" Black Holes May Roam Milky Way

January 10, 2008

Newly merged black holes might be so jarred by the experience that they go "rogue," careening into space on unexpected trajectories.

In fact, hundreds of these rogue black holes could exist in the Milky Way galaxy alone, according to a new study.

The research is just one of several new findings on black holes presented Wednesday at a meeting of the American Astronomical Society in Austin, Texas.

Together, the observations are helping unravel some mysteries of the superdense objects—while simultaneously offering perplexing new puzzles.

Scientists at the presentation, for instance, offered up new explanations about odd x-ray sources coming from black holes.

They also found hints that dark matter may play an important role in the hot disks that form around companion-consuming black holes.

Black Hole Billiards

Astronomers have long known about rogue black holes.

But Kelly Holley-Bockelmann, of Tennessee's Vanderbilt University, and her colleagues were the first to show that the objects could arise from violent mergers.

Using a computer model, Holley-Bockelmann found that two combining black holes rotating at different speeds or of different sizes give the newly merged black hole a big kick.

This sends the object hurtling in an arbitrary direction at velocities as high as 2,485 miles (4,000 kilometers) per second.

"This is much higher than anyone predicted," Holley-Bockelmann said. "Even the average kick velocity of 200 kilometers [124 miles] per second is extremely high."

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