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Giant Black Hole Kicked Out of Home Galaxy

For Release: June 4, 2012


Credit: X-ray: NASA/CXC/SAO/F.Civano et al; Optical: NASA/STScI; Optical (wide field): CFHT, NASA/STScI
Press Image and Caption

WASHINGTON — Astronomers have found strong evidence that a massive black hole is being ejected from its host galaxy at a speed of several million miles per hour. New observations from NASA's Chandra X-ray Observatory suggest that the black hole collided and merged with another black hole and received a powerful recoil kick from gravitational wave radiation.

"It's hard to believe that a supermassive black hole weighing millions of times the mass of the sun could be moved at all, let alone kicked out of a galaxy at enormous speed," said Francesca Civano of the Harvard-Smithsonian Center for Astrophysics (CfA), who led the new study. "But these new data support the idea that gravitational waves -- ripples in the fabric of space first predicted by Albert Einstein but never detected directly -- can exert an extremely powerful force."

Although the ejection of a supermassive black hole from a galaxy by recoil because more gravitational waves are being emitted in one direction than another is likely to be rare, it nevertheless could mean that there are many giant black holes roaming undetected out in the vast spaces between galaxies.

"These black holes would be invisible to us," said co-author Laura Blecha, also of CfA, "because they have consumed all of the gas surrounding them after being thrown out of their home galaxy."

Civano and her group have been studying a system known as CID-42, located in the middle of a galaxy about 4 billion light years away. They had previously spotted two distinct, compact sources of optical light in CID-42, using NASA's Hubble Space Telescope.

More optical data from the ground-based Magellan and Very Large Telescopes in Chile supplied a spectrum (that is, the distribution of optical light with energy) that suggested the two sources in CID-42 are moving apart at a speed of at least 3 million miles per hour.

Previous Chandra observations detected a bright X-ray source likely caused by super-heated material around one or more supermassive black holes. However, they could not distinguish whether the X-rays came from one or both of the optical sources because Chandra was not pointed directly at CID-42, giving an X-ray source that was less sharp than usual.

"The previous data told us that there was something special going on, but we couldn't tell if there were two black holes or just one," said another co-author Martin Elvis, also of CfA. "We needed new X-ray data to separate the sources."

When Chandra's sharp High Resolution Camera was pointed directly at CID-42, the resulting data showed that X-rays were coming only from one of the sources. The team thinks that when two galaxies collided, the supermassive black holes in the center of each galaxy also collided. The two black holes then merged to form a single black hole that recoiled from gravitational waves produced by the collision, which gave the newly merged black hole a sufficiently large kick for it to eventually escape from the galaxy. The other optical source is thought to be the bright star cluster that was left behind. This picture is consistent with recent computer simulations of merging black holes, which show that merged black holes can receive powerful kicks from the emission of gravitational waves.

There are two other possible explanations for what is happening in CID-42. One would involve an encounter between three supermassive black holes, resulting in the lightest one being ejected. Another idea is that CID-42 contains two supermassive black holes spiraling toward one another, rather than one moving quickly away.

Both of these alternate explanations would require at least one of the supermassive black holes to be very obscured, since only one bright X-ray source is observed. Thus the Chandra data support the idea of a black hole recoiling because of gravitational waves.

The source is located in the Cosmic Evolution Survey (COSMOS) field, a large, multi-wavelength survey. The other co-authors are Giorgio Lanzuisi (CfA, MPE), Thomas Aldcroft (CfA), Markos Trichas (CfA), Angela Bongiorno (MPE), Marcella Brusa (MPE), Andrea Comastri (INAF, Bologna, Italy), Avi Loeb (Harvard University), Mara Salvato (MPE), Antonella Fruscione (CfA), Anton Koekemoer (STSCI), Stefanie Komossa (TUM ExC/IPP, Germany), Roberto Gilli (INAF, Bologna, Italy), Vincenzo Mainieri (ESO), Enrico Piconcelli (ESA), Cristian Vignali (Bologna University).

These results will appear in the June 10 issue of The Astrophysical Journal. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra Program for the agency's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Mass., controls Chandra's science and flight operations.

For Chandra images, multimedia and related materials, visit:

For an additional interactive image, podcast, and video on the finding, visit:

Media contacts:
J.D. Harrington
Headquarters, Washington

Megan Watzke
Chandra X-ray Center, Cambridge, Mass.

Visitor Comments (8)

Perhaps something was missed. The ejected SMBH possibly interacted with two other SMBHs. Binary pairs tend to simply merge, depending on trajectory and velocity the presence of a third may better explain the image.

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Posted by Winstrol 2 mg on Sunday, 03.24.13 @ 06:30am

I believe the black hole is being pulled into another much bigger black hole. It is not being ejected instead think of it more like if our solar system were to lose speed and stop orbiting sagittarius A* we would no longer be able to escape its gravity and we would be pulled straight in.

Posted by Jon Canning on Friday, 09.28.12 @ 04:31am

Cavitation: new physics term for me though I observed it frequently.
Question: can gravity cavitate? I some degree its turbulence, but in the shape of a trail.

Posted by Jim Hinton on Wednesday, 06.6.12 @ 15:51pm

The video was very helpful in demonstrating what occurrs when two black holes collide.

Posted by Mariposa on Tuesday, 06.5.12 @ 22:58pm

Eventually, the ejected massive black hole would have no stars around it and cannot be seen in any light, X-ray or visible. How do we know how many of these solitary black holes are there in our universe?

Posted by S. Paul Pao on Tuesday, 06.5.12 @ 09:40am

Totally awesome! Thank you all for your work and bringing us into the universe of the unknown and your help in making it known.
Congrats and a big thank you.

Posted by Don Schipani on Monday, 06.4.12 @ 23:08pm