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NASA's Chandra Turns up Black Hole Bonanza in Galaxy Next Door

For Release: June 12, 2013


Credit: X-ray (NASA/CXC/SAO/R.Barnard, Z.Lee et al.), Optical (NOAO/AURA/NSF/REU Prog./B.Schoening, V.Harvey; Descubre Fndn./CAHA/OAUV/DSA/V.Peris)
Press Image and Caption

WASHINGTON -- Using data from NASA's Chandra X-ray Observatory, astronomers have discovered an unprecedented bonanza of black holes in the Andromeda Galaxy, one of the nearest galaxies to the Milky Way.

Using more than 150 Chandra observations, spread over 13 years, researchers identified 26 black hole candidates, the largest number to date, in a galaxy outside our own. Many consider Andromeda to be a sister galaxy to the Milky Way. The two ultimately will collide, several billion years from now.

"While we are excited to find so many black holes in Andromeda, we think it's just the tip of the iceberg," said Robin Barnard of Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass., and lead author of a new paper describing these results. "Most black holes won't have close companions and will be invisible to us."

The black hole candidates belong to the stellar mass category, meaning they formed in the death throes of very massive stars and typically have masses five to 10 times that of our sun. Astronomers can detect these otherwise invisible objects as material is pulled from a companion star and heated up to produce radiation before it disappears into the black hole.

The first step in identifying these black holes was to make sure they were stellar mass systems in the Andromeda Galaxy itself, rather than supermassive black holes at the hearts of more distant galaxies. To do this, the researchers used a new technique that draws on information about the brightness and variability of the X-ray sources in the Chandra data. In short, the stellar mass systems change much more quickly than the supermassive black holes.

To classify those Andromeda systems as black holes, astronomers observed that these X-ray sources had special characteristics: that is, they were brighter than a certain high level of X-rays and also had a particular X-ray color. Sources containing neutron stars, the dense cores of dead stars that would be the alternate explanation for these observations, do not show both of these features simultaneously. But sources containing black holes do.

The European Space Agency's XMM-Newton X-ray observatory added crucial support for this work by providing X-ray spectra, the distribution of X-rays with energy, for some of the black hole candidates. The spectra are important information that helps determine the nature of these objects.

"By observing in snapshots covering more than a dozen years, we are able to build up a uniquely useful view of M31," said co-author Michael Garcia, also of CfA. "The resulting very long exposure allows us to test if individual sources are black holes or neutron stars."

The research group previously identified nine black hole candidates within the region covered by the Chandra data, and the present results increase the total to 35. Eight of these are associated with globular clusters, the ancient concentrations of stars distributed in a spherical pattern about the center of the galaxy. This also differentiates Andromeda from the Milky Way as astronomers have yet to find a similar black hole in one of the Milky Way's globular clusters.

Seven of these black hole candidates are within 1,000 light-years of the Andromeda Galaxy's center. That is more than the number of black hole candidates with similar properties located near the center of our own galaxy. This is not a surprise to astronomers because the bulge of stars in the middle of Andromeda is bigger, allowing more black holes to form.

"When it comes to finding black holes in the central region of a galaxy, it is indeed the case where bigger is better," said co-author Stephen Murray of Johns Hopkins University and CfA. "In the case of Andromeda we have a bigger bulge and a bigger supermassive black hole than in the Milky Way, so we expect more smaller black holes are made there as well."

This new work confirms predictions made earlier in the Chandra mission about the properties of X-ray sources near the center of M31. Earlier research by Rasmus Voss and Marat Gilfanov of the Max Planck Institute for Astrophysics in Garching, Germany, used Chandra to show there was an unusually large number of X-ray sources near the center of M31. They predicted most of these extra X-ray sources would contain black holes that had encountered and captured low mass stars. This new detection of seven black hole candidates close to the center of M31 gives strong support to these claims.

"We are particularly excited to see so many black hole candidates this close to the center, because we expected to see them and have been searching for years," said Barnard.

These results are available online and will be published in the June 20 issue of The Astrophysical Journal. Many of the Andromeda observations were made within Chandra's Guaranteed Time Observer program.

NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra Program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.

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 (22)

I agree with Ron's post on 6-13-13 at 8 58 am. Since energy cannot be created or destroyed, I believe the big bang is the result of a expired universe or maybe somehow black holes are involved in creating a big bang.

Posted by Mark on Tuesday, 06.6.17 @ 10:39am

A black hole in any of the pictures shown of any galaxy looks white... Strange misnomer.

Posted by Yathiender Sridharan on Friday, 11.27.15 @ 06:39am

The image of Andromeda galaxy is super. I appreciate all the information allied with Andromeda. I was surprised to learn that it has 35 black holes candidates which were caused by the collapse of a giant star. The collapse of one massive star may create many black holes is what I learned afresh. well, how many black hole candidates are in our Milky Way galaxy?

Posted by Dravida shaan on Saturday, 08.22.15 @ 11:10am

This is an amazing experience, I only see it in my imagination.

Posted by DUNCAN WOLF on Wednesday, 10.22.14 @ 12:53pm

This information is really great. But my question has nothing to do with the above. If someone happen to read my comment and could answer my question, please don t hesitate to write an e-mail to me. Anyway, my question is Are there anti-matter swirling in black holes?

Posted by Ricki Warmheart on Monday, 07.21.14 @ 12:39pm

It's always amazing and incredible. Thanks a lot. I could never imagine that our neighbor will have a such number of black holes near its center. I am really fascinated with that, but I need more, it is like a part is missing to explain more this phenomenon.

Posted by NASAFan on Tuesday, 07.15.14 @ 08:18am

More info please. I had to write a 3 paragraph essay about this but I did not have enough info. Thanks so much.

Posted by hinksdt heart on Tuesday, 04.1.14 @ 22:19pm

This includes grate information, but I need more.

Posted by Manage on Friday, 12.27.13 @ 14:09pm

It urges you to go out there and observe them from the nearest possible distance these pictures. I hope we develop the technology, in my life time, to get to all these stars we see or may be get out of our solar system in one life time or may be less, it will be fascinating.

Posted by Lovish on Thursday, 11.14.13 @ 16:15pm

I see where scientists say "galaxies with black holes", does that mean that there are some galaxies without black holes? if there are, then what the heck is keeping all those stars spiraling together? I know its a mystery how the black holes are affecting the stars at the edges of galaxies, but just wondering about those without black holes. Fascinating universe. AWESOME

Posted by chad on Monday, 11.4.13 @ 02:10am

Beautiful photographs and really great observation.

Posted by kalpesh on Sunday, 07.28.13 @ 00:41am

Black hole is important projection for future.

Posted by elsanosse on Saturday, 07.13.13 @ 15:14pm

Kolya's theory of black holes forming one big black hole is fascinating. What do you suppose is the time scale of the first BANG to the second BANG? Are we in a never ending cycle?

Posted by John F Gans on Monday, 06.24.13 @ 11:20am

If a supernova explodes, does the amount of matter emitted from the explosion equal the original mass, or is there something missing? Unless we physically see one happening and know what was there before, is it possible that all we are seeing is the sudden emission from super massive black hole?

Posted by Andy on Monday, 06.17.13 @ 06:24am

Fantastic imagery. Thank you!

Posted by Phil Huff on Saturday, 06.15.13 @ 10:11am

Black holes are very interesting to read and see in NASA's Chandra X-ray Observatory. 26 of black hole candidate is not so few.

Posted by Heljo Valter on Friday, 06.14.13 @ 12:28pm

Wow, and where do we keep going?

Posted by rick moll on Friday, 06.14.13 @ 04:11am

I think all of the black hole is time to unite and map of the galaxy. It will give scientists time to monitor their dynamics and location.

Posted by Alex Kulay on Thursday, 06.13.13 @ 23:50pm

I appreciate this and other articles from NASA.
I wish we could travel faster than light, but I believe Dr. Einstein ruled that out many years ago. Always wonder what these distant objects look like now.

Posted by Steve Webb on Thursday, 06.13.13 @ 12:23pm

Want to see more.

Posted by gray kolya on Thursday, 06.13.13 @ 09:00am

It appears to me, that, eventually all the black holes will join up
in every galaxy, with gravity being so powerful, all the galaxies
will be attracted to each other, and all the black holes will eventually
join together to form one black hole, and then BANG a new Universe.

Posted by RON on Thursday, 06.13.13 @ 08:58am

Very important information &great photos

Posted by Rajika RUwini on Thursday, 06.13.13 @ 02:49am