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Hubble research reveals galaxy’s ‘wandering’ black hole

Hubble Space Telescope Images of M87

A team of scientists from the University of Sussex and in the USA, who are closely observing the centres of nearby galaxies, have discovered that one of the most famous supermassive black holes is on the move.

The discovery, made through observations of Hubble Space Telescope (HST) data, will help scientists refine their understanding of how galaxies are made and how they evolve.

Messier 87 is a massive elliptical galaxy that, at 60 million light years' distance from Earth, is our most impressive and closest galactic neighbour. It is distinctive for its brilliant and dense nebulae of stars and a distinctive 'jet' of sub-atomic particles that is propelled from its active centre.

A team of astronomy researchers at the University of Sussex, the Florida Institute of Technology and Rochester Institute of Technology in the United States have found that the supermassive black hole (SMBH) thought to be at the centre of M87 has actually been displaced.

The most likely cause, says Florida Institute of Technology's assistant professor Daniel Batcheldor, who led the investigation, is a previous merger between two older, less massive, SMBHs, but it may also be down to the propulsive energy of M87's iconic jet.

The study of M87 is part of a wider HST project directed by Andrew Robinson, professor of physics at RIT, who says: "The possibility is that we have found a signpost to a black hole merger, which is of interest to people looking for gravitational waves and those modeling these systems as a demonstration that black holes really do merge.

"The theoretical prediction is that when two black holes merge, the newly combined black hole receives a 'kick' due to the emission of gravitational waves, which can displace it from the centre of the galaxy."

David Merritt, professor of physics at RIT, adds: "Once kicked, a supermassive black hole can take millions or billions of years to return to rest, especially at the centre of a large, diffuse galaxy such as M87. So searching for displacements is an effective way to constrain the merger history of galaxies."

Many galaxies have similar properties to M87, so it is likely that SMBHs are commonly offset from their host galaxy centres. Professor David Axon, who is head of the School of Mathematical and Physical Sciences at the University of Sussex, says: "In current galaxy formation scenarios galaxies are thought to be assembled by a process of merging. We should therefore expect that binary black holes and post coalescence recoiling black holes, like that in M87, are very common in the cosmos."

Earth's own galaxy is predicted to merge with the Andromeda galaxy, which could then result in a similar wandering SMBH at the heart of the new galaxy - in about 3 billion years' time.

Notes for Editors

The research will be presented at the American Astronomical Society (AAS) Conference on Tuesday 25 May in Miami, Florida, USA and will be published in 'A Displaced Supermassive Black Hole in M87', D. Batcheldor, E. Perlman (Florida Institute of Technology, USA); A. Robinson, D. Merritt (Rochester Institute of Technology, USA) and D. Axon, University of Sussex, UK, Astrophysical Journal Letters (May 2010


Above: Hubble Space Telescope Images of M87. At right, a large scale image taken with the Wide-Field/Planetary Camera-2 from 1998 (NASA and the Hubble Heritage Team (STScI/AURA), J. A. Biretta, W. B. Sparks, F. D. Macchetto, E. S. Perlman). The two images at left show an image taken in 2006 with the Advanced Camera for Surveys' High Resolution Channel. The position of the supermassive black hole is indicated by the black dot in the lower left panel, and a knot in the jet (HST-1), which was flaring in 2006, is also indicated on this panel. The red dot indicates the center of the galaxy's light distribution, which is offset from the position of the black hole by 22 +/- 3 light years.

Home page image: Hubble Space Telescope image of M87 using the Wide Field Channel of the Advanced Camera for Surveys (ACS). The image was taken as part of the ACS Virgo Cluster Survey led by P. Côté of the Dominion Astrophysics Observatory. See for more details.

See: to download a copy of the paper.

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Last updated: Tuesday, 25 May 2010