Natural Science Forum / Physics / General Physics / May 2007

PHYSICAL REVIEW FOCUS   30 May 2007   http://focus.aps.org/
David Ehrenstein, American Physical Society

Introductions to the Focus stories of the past week;
visit http://focus.aps.org for the complete stories.

INTERGALACTIC PROJECTILES
When two black holes merge, they make waves--powerful gravitational
waves. And if the merger spews these waves preferentially in one direction,
it can shoot the merged hole the other way at high speed. In an upcoming
issue of Physical Review Letters, two teams use computer simulations to
show that the recoil speed for a pair of "supermassive" black holes could
reach 4000 kilometers per second--ten times faster than previous estimates
and fast enough to escape from even the biggest galaxy. Such a "black hole
rocket" would be nearly invisible, but in some cases, according to a study in
another upcoming issue of Physical Review Letters, it might be observable if
it brings enough material from the galaxy along with it.
(Jose A. Gonzalez et al., Phys. Rev. Lett. to be published)
(Manuela Campanelli et al., Phys. Rev. Lett. to be published)
(Abraham Loeb, Phys. Rev. Lett. to be published)
COMPLETE Focus story at http://focus.aps.org/story/v19/st17

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Copyright 2007, The American Physical Society.