Monster Black Hole Mergers May Be Common

The spiral galaxies UGC 9618 and VV 340, which are about to collide. Astronomers believe such galaxy mergers also usually involve the merger of the supermassive black holes at galaxies’ cores. Credit: NASA, ESA, the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration, and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University)
The collision of black holes harboring millions or billions of times the mass of the sun are likely common throughout the universe, a new study suggests.

By Mike Wall |

Such supermassive black holes lurk at the heart of most, if not all, galaxies, including our own Milky Way. Galaxy mergers are common throughout the universe, and astronomers think that such mashups usually involve the merger of the gigantic central black holes as well.

But evidence of such collisions has been elusive to date. For example, the gravitational waves emitted in the lead-up to monster black hole mergers are likely outside the range of those detectable by the Laser Interferometer Gravitational-wave Observatory (LIGO). The gravitational waves spotted by LIGO to date were emitted by merging objects that each harbored no more than a few dozen solar masses. [Hunting Gravitational Waves: The LIGO Laser Interferometer Project in Photos]

So, in the new study, researchers took a different tack. They analyzed radio-wavelength observations of 33 sources of powerful jets, features commonly associated with supermassive black holes. In 24 of those sources, the team saw signs of „precession,“ or a change in the orientation of the axis of rotation.

This came as a surprise, said study lead author Martin Krause, of the University of Hertfordshire in England.

„We have studied the jets in different conditions for a long time with computer simulations,“ Krause said in a statement. „In this first systematic comparison to high-resolution radio maps of the most powerful radio sources, we were astonished to find signatures that were compatible with jet precession in three-quarters of the sources.“

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