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Gravitational Kick

October 24, 2012

Gravitational waves are so weak that no one has yet discovered a single one. Yet if you gang up enough of them, their effect can be profound — strong enough to kick a supermassive black hole out of its home galaxy, for example.

Gravitational waves are produced by the motion of any object with mass — from fireflies to fiery stars. They’re so extremely weak, however, that it takes the motion of an extremely massive object to produce any detectable effect at all. Astronomers have detected the signature of gravitational waves in the changing orbits of pairs of dense stellar corpses known as neutron stars, for example.

They’ve also detected the likely result of gravitational waves in the heart of a galaxy that’s about four billion light-years away.

Observations by ground- and space-based telescopes revealed two large, compact objects near the center of the galaxy that are moving away from each other at about three million miles an hour. Follow-up observations suggest that one is a supermassive black hole, while the other is a star cluster.

Astronomers suspect that the galaxy formed from the merger of two smaller galaxies. The black holes at the centers of these galaxies also merged, forming an even bigger black hole. But the way the black holes merged produced a torrent of gravitational waves — enough to send the combined black hole skittering out of the galaxy at millions of miles an hour.

More about black holes tomorrow.


Script by Damond Benningfield, Copyright 2012

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