Milky Way galaxy may be host to hundreds of "rogue" black holes

Washington, Jan 10 : Computer simulations have suggested that there might be hundreds of rogue black holes roaming around the Milky Way galaxy, which might weigh several thousand times the mass of the sun.he simulation was developed by a supercomputer at Vanderbilt University, Nashville, US, with much of the research done at Penn State University.

In the past two years, scientists have succeeded in numerically simulating black hole mergers that incorporate Einstein's theory of relativity.

One of the big surprises to come from this effort is the prediction that when two black holes that are rotating at different speeds or are different sizes combine, the newly merged black hole receives a big kick due to conservation of momentum, pushing it away in an arbitrary direction at velocities as high as 4,000 kilometers per second.

This fact made the researchers refer the black holes as to being "rogue" in nature.

"This is much higher than anyone predicted. Even the average kick velocity of 200 kilometers per second is extremely high when compared to the escape velocities of typical astronomical objects," said Vanderbilt astronomer Kelly Holley-Bockelmann.

"We realized that basically any black hole merger would kick the new remnant out of a globular cluster, because the escape velocity is less than 100 kilometers per second," he added.

As for the research, it focused on modeling "intermediate mass" black holes, whose very existence is controversial.

Theoreticians have predicted that globular clusters - ancient, gravitationally bound groups of 100,000 to a million stars - should contain a third class of black holes, called intermediate mass black holes, that weigh a few thousand solar masses.

If the roughly 200 globular clusters in the Milky Way have indeed spawned intermediate-sized black holes, this means that hundreds of them are probably wandering invisibly around the Milky Way, waiting to engulf the nebulae, stars and planets that are unfortunate enough to cross their paths.

But, the existence of a few rogue black holes in the neighborhood does not present a major danger.

"These rogue black holes are extremely unlikely to do any damage to us in the lifetime of the universe," said Holley-Bockelmann. "Their danger zone, the Schwarzschild radius, is really tiny, only a few hundred kilometers," he added.

ANI