Space

June 12, 2013

NASA’s Chandra turns up black hole bonanza in galaxy next door

nasa-chandra
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 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.

 




All of this week's top headlines to your email every Friday.


 
 

 

Headlines November 26, 2014

News: When Hagel leaves, new SecDef faces big questions about the military’s future - President Obama’s new pick to run the Pentagon will face a dizzying set of challenges affecting the Defense Department’s mission, budget and culture. Who will be the next Secretary of Defense?- Following the Nov. 24 surprise announcement from the White House, the...
 
 

News Briefs November 26, 2014

Navy to decommission two more ships in Puget Sound The Navy recently decommissioned the guided missile frigate USS Ingraham at Everett, Wash. It will be towed to Bremerton and scrapped. The Daily Herald reports the Navy also plans to decommission another ship at the Everett homeport and also one stationed in Bremerton. Naval Station Everett...
 
 

NASA airborne campaigns tackle climate questions from Africa to Arctic

NASA photograph The DC-8 airborne laboratory is one of several NASA aircraft that will fly in support of five new investigations into how different aspects of the interconnected Earth system influence climate change. NASA photograph The DC-8 airborne laboratory is one of several NASA aircraft that will fly in support of five new investigations into...
 

 
Air Force photograph by Rick Goodfriend

16T Pitch Boom reactivated to support wind tunnel tests

Air Force photograph by Rick Goodfriend The Pitch Boom at the AEDC 16-foot transonic wind tunnel (16T) was recently reactivated. This model support system is used in conjunction with a roll mechanism to provide a combined pitch...
 
 

Northrop Grumman supports U.S. Air Force Minuteman missile test launch

Northrop Grumman recently supported the successful flight testing of the U.S. Air Force’s Minuteman III intercontinental ballistic missile weapon system. The operational flight test was conducted as part of the Air Force Global Strike Command’s Force Development Evaluation Program. This program demonstrates and supports assessment of the accuracy, availability and reliability of the...
 
 
army-detector

Scientists turn handheld JCAD into a dual-use chemical, explosives detector

Scientists at the U.S. Army Edgewood Chemical Biological Center at Aberdeen Proving Ground, Md., proved it is possible to teach an old dog new tricks by adding the ability to detect explosive materials to the Joint Chemical Age...
 




0 Comments


Be the first to comment!


Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>