Astronomers discover close-knit pairs of massive black holes
Astronomers at the California Institute of Technology (Caltech), University of Illinois at Urbana-Champaign (UIUC), and University of Hawaii (UH) have discovered 16 close-knit pairs of supermassive black holes in merging galaxies. The discovery, based on observations done at the W. M. Keck Observatory on Hawaii's Mauna Kea, is being presented in Seattle on January 12 at the meeting of the American Astronomical Society, and has been submitted for publication in the Astrophysical Journal.
These black-hole pairs, also called binaries, are about a hundred to a thousand times closer together than most that have been observed before, providing astronomers a glimpse into how these behemoths and their host galaxies merge—a crucial part of understanding the evolution of the universe. Although few similarly close pairs have been seen previously, this is the largest population of such objects observed as the result of a systematic search.
"This is a very nice confirmation of theoretical predictions," says S. George Djorgovski, professor of astronomy, who will present the results at the conference. "These close pairs are a missing link between the wide binary systems seen previously and the merging black-hole pairs at even smaller separations that we believe must be there."
As the universe has evolved, galaxies have collided and merged to form larger ones. Nearly every one—or perhaps all—of these large galaxies contains a giant black hole at its center, with a mass millions—or even billions—of times higher than the sun's. Material such as interstellar gas falls into the black hole, producing enough energy to outshine galaxies composed of a hundred billion stars. The hot gas and black hole form an active galactic nucleus, the brightest and most distant of which are called quasars. The prodigious energy output of active galactic nuclei can affect the evolution of galaxies themselves.
While galaxies merge, so should their central black holes, producing an even more massive black hole in the nucleus of the resulting galaxy. Such collisions are expected to generate bursts of gravitational waves, which have yet to be detected. Some merging galaxies should contain pairs of active nuclei, indicating the presence of supermassive black holes on their way to coalescing. Until now, astronomers have generally observed only widely separated pairs—binary quasars—which are typically hundreds of thousands of light-years apart.
"If our understanding of structure formation in the universe is correct, closer pairs of active nuclei must exist," adds Adam Myers, a research scientist at UIUC and one of the coauthors. "However, they would be hard to discern in typical images blurred by Earth's atmosphere."
The solution was to use Laser Guide Star Adaptive Optics, a technique that enables astronomers to remove the atmospheric blur and capture images as sharp as those taken from space. One such system is deployed on the W. M. Keck Observatory's 10-meter telescopes on Mauna Kea.
The astronomers selected their targets using spectra of known galaxies from the Sloan Digital Sky Survey (SDSS). In the SDSS images, the galaxies are unresolved, appearing as single objects instead of binaries. To find potential pairs, the astronomers identified targets with double sets of emission lines—a key feature that suggests the existence of two active nuclei.
By using adaptive optics on Keck, the astronomers were able to resolve close pairs of galactic nuclei, discovering 16 such binaries out of 50 targets. "The pairs we see are separated only by a few thousands of light-years—and there are probably many more to be found," says Hai Fu, a Caltech postdoctoral scholar and the lead author of the paper.
"Our results add to the growing understanding of how galaxies and their central black holes evolve," adds Lin Yan, a staff scientist at Caltech and one of the coauthors of the study.
"These results illustrate the discovery power of adaptive optics on large telescopes," Djorgovski says. "With the upcoming Thirty Meter Telescope, we'll be able to push our observational capabilities to see pairs with separations that are three times closer."
Articles on the same topic
- Taking the pulse of a black hole systemWed, 12 Jan 2011, 17:33:30 EST
- Surprise: Dwarf galaxy harbors supermassive black holeSun, 9 Jan 2011, 13:51:26 EST
- Astronomers calculate mass of largest black hole yetfrom PhysorgFri, 14 Jan 2011, 18:00:19 EST
- Taking the pulse of a black hole systemfrom Science DailyThu, 13 Jan 2011, 23:30:42 EST
- At 6.6 Billion Suns, The Largest Black Hole Ever Measured Could Swallow Our Solar Systemfrom PopSciThu, 13 Jan 2011, 16:20:36 EST
- Astronomers discover close-knit pairs of massive black holesfrom Science CentricThu, 13 Jan 2011, 12:22:17 EST
- Taking the Pulse of a Black Hole Systemfrom Newswise - ScinewsWed, 12 Jan 2011, 22:30:22 EST
- Astronomers discover 16 black-hole pairsfrom UPIWed, 12 Jan 2011, 19:50:11 EST
- Taking the pulse of a black hole systemfrom Science BlogWed, 12 Jan 2011, 19:30:37 EST
- Most Massive Black Hole Known Tips Scales at 6.6 Billion Sunsfrom Space.comWed, 12 Jan 2011, 19:30:19 EST
- Taking the pulse of a black hole system (w/ Video)from PhysorgWed, 12 Jan 2011, 18:50:14 EST
- Neighboring black hole puts on weightfrom Sciencenews.orgWed, 12 Jan 2011, 18:30:18 EST
- Tiny Galaxy Hiding a Big Secretfrom CBSNews - ScienceWed, 12 Jan 2011, 14:41:03 EST
- Close-knit pairs of supermassive black holes discovered in merging galaxiesfrom Science DailyWed, 12 Jan 2011, 14:21:35 EST
- Astronomers discover close-knit pairs of massive black holesfrom PhysorgWed, 12 Jan 2011, 13:52:46 EST
- Tiny Galaxy Hiding a Big Secretfrom CBSNews - ScienceWed, 12 Jan 2011, 11:30:23 EST
- Mystery Deepens in Origin of Violent Black Holesfrom Space.comTue, 11 Jan 2011, 16:03:04 EST
- Ginormous Black Hole May Solve Longstanding Mysteryfrom Space.comTue, 11 Jan 2011, 16:01:40 EST
- Dwarf galaxy solves supermassive mysteryfrom Physics WorldMon, 10 Jan 2011, 17:20:12 EST
- Huge Black Hole Found in Dwarf Galaxyfrom National GeographicMon, 10 Jan 2011, 14:00:09 EST
- Physicists create sonic black hole in the labfrom PhysorgMon, 10 Jan 2011, 9:00:24 EST
- Surprise: Dwarf galaxy harbors supermassive black holefrom Science BlogMon, 10 Jan 2011, 3:20:08 EST
- Dwarf galaxy harbors supermassive black holefrom Science DailySun, 9 Jan 2011, 21:30:20 EST
- Surprise: Dwarf galaxy harbors supermassive black holefrom PhysorgSun, 9 Jan 2011, 14:50:49 EST
- Surprise: Dwarf galaxy harbours supermassive black holefrom Science CentricSun, 9 Jan 2011, 14:40:14 EST
- Hole's on First?: New Evidence Shows Black Hole Growth Preceding Galactic Formationfrom Scientific AmericanSun, 9 Jan 2011, 14:00:27 EST
- Ginormous Black Hole May Solve Longstanding Mysteryfrom Space.comSun, 9 Jan 2011, 13:50:23 EST
Latest Science NewsletterGet the latest and most popular science news articles of the week in your Inbox! It's free!
Learn more about
Check out our next project, Biology.Net
From other science news sites
Popular science news articles
- Scientists reveal the secret of antibiotic-resistant bacteria
- A cleansing rain falls; a soil-filled mist arises
- Concussion outcomes differ among football players from youth to college
- US climate-adaptation plans long on ideas, short on details, priorities
- New interpretation of the Rök runestone inscription changes view of Viking Age