Rogue Black Holes
Astronomers are hunting an elusive target: rogue black holes that have been ejected from the centers of their home galaxies.
Some doubted that the quarry could be spotted, since a black hole must be gobbling matter from an accretion disk in order for that matter to shine. (Image Credit: NASA)
And if a black hole is ripped from the core of its home galaxy and sent hurling into the outskirts, the thinking goes, then its accretion disk might be left behind.
New calculations by theorist Avi Loeb (Harvard-Smithsonian Center for Astrophysics) give black hole hunters a reason to hope. Loeb showed that, generically, a black hole ejected from the center of a galaxy could bring its accretion disk along for the ride and remain visible for millions of years.
"Matter in the disk is swirling around the black hole much faster than the typical black-hole ejection speed. That matter is so tightly bound that it follows the black hole like a herd of sheep around a shepherd," said Loeb.
In the scenario examined by Loeb, two galaxies collide and merge. The spinning, supermassive black holes at the core of each galaxy coalesce, emitting powerful gravitational radiation in a preferred direction. Computer simulations recently demonstrated that the net momentum carried by the radiation gives the remnant black hole a large kick in the opposite direction. The black hole recoils at speeds of up to ten million miles per hour -- fast enough to traverse an entire galaxy in a cosmically short time of only ten million years.
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Survival time inside the event horizon of a black hole from Universe Today
No Way Back: Maximizing survival time below the Schwarzschild event horizon
GRB's active longer than previously thought from Science Daily