This Vanderbilt Exploration story reveals that hundreds of rogue black holes could be roaming our galactic neighborhood.
From editor and writer David Salisbury’s story:
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.
If [the modeling is correct], and 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.
Fortunately, 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,” says Vanderbilt astronomer Kelly Holley-Bockelmann. “Their danger zone, the Schwarzschild radius, is really tiny, only a few hundred kilometers. There are far more dangerous things in our neighborhood!”