 |
|
Galaxy may hold hundreds of rogue black holes
January 10, 2008If the latest simulation of what happens when black holes merge is correct, there could be hundreds of rogue black holes, each weighing several thousand times the mass of the sun, roaming around the Milky Way galaxy.
"Rogue black holes like this would be very difficult to spot," says Vanderbilt astronomer Kelly Holley-Bockelmann, who is presenting the results of the supercomputer simulation at a meeting of the American Astronomical Society on Jan. 9 in Austin, Texas. Much of the research was done at Penn State University in collaboration with Deirdre Shoemaker and Nicolas Yunes before Holley-Bockelmann moved to Vanderbilt. Kayhan Gultekin at the University of Michigan also participated in the study.
"Unless it's swallowing a lot of gas, about the only way to detect the approach of such a black hole would be to observe the way in which its super-strength gravitational field bends the light that passes nearby. This produces an effect called gravitational lensing that would make background stars appear to shift and brighten momentarily," she says.
The research focused on modeling "intermediate mass" black holes, whose very existence is controversial. Astronomers have ample evidence that small black holes less than 100 solar masses are produced when giant stars explode. There is similar evidence that "super-massive" black holes weighing the equivalent of millions to billions of solar masses sit at the heart of many galaxies, including the Milky Way. In addition, theoreticians have predicted that globular clusters - ancient, gravitationally bound groups of 100,000 to a million stars - should contain a third class of black holes, called intermediate mass black holes, that weigh a few thousand solar masses. But so far there have only been two tentative observations of objects of this sort.
In the past two years, scientists have succeeded in numerically simulating black hole mergers that incorporate Einstein's theory of relativity. One of the big surprises to come from this effort is the prediction that when two black holes that are rotating at different speeds or are different sizes combine, the newly merged black hole receives a big kick due to conservation of momentum, pushing it away in an arbitrary direction at velocities as high as 4,000 kilometers per second.
"This is much higher than anyone predicted. Even the average kick velocity of 200 kilometers per second is extremely high when compared to the escape velocities of typical astronomical objects," says Holley-Bockelmann. "We realized that basically any black hole merger would kick the new remnant out of a globular cluster, because the escape velocity is less than 100 kilometers per second."
Using the facilities of Vanderbilt's Advanced Center for Computation, Research and Education, Holley-Bockelmann's team ran a number of simulations of the growth of intermediate mass black holes as they combine with a number of stellar-sized black holes, which are plentiful in globular clusters, paying close attention to the kick they received after each merger.
"We used different assumptions for the initial black hole mass, for the range of stellar black hole masses within a globular cluster, and assumed that the spins and spin orientations were distributed randomly. With our most conservative assumptions, we found that, even if every globular cluster started out with an intermediate-sized black hole, only about 30 percent retain them through the merger epoch. With our least conservative assumptions, less than 2 percent of the globular clusters should contain intermediate mass black holes today," she says.
If the roughly 200 globular clusters in the Milky Way have indeed spawned intermediate-sized black holes, this means that hundreds of them are probably wandering invisibly around the Milky Way, waiting to engulf the nebulae, stars and planets that are unfortunate enough to cross their paths.
Fortunately, the existence of a few rogue black holes in the neighborhood does not present a major danger. "These rogue black holes are extremely unlikely to do any damage to us in the lifetime of the universe," Holley-Bockelmann stresses. "Their danger zone, the Schwarzschild radius, is really tiny, only a few hundred kilometers. There are far more dangerous things in our neighborhood!"
Vanderbilt University
The research focused on modeling "intermediate mass" black holes, whose very existence is controversial. Astronomers have ample evidence that small black holes less than 100 solar masses are produced when giant stars explode. There is similar evidence that "super-massive" black holes weighing the equivalent of millions to billions of solar masses sit at the heart of many galaxies, including the Milky Way. In addition, theoreticians have predicted that globular clusters - ancient, gravitationally bound groups of 100,000 to a million stars - should contain a third class of black holes, called intermediate mass black holes, that weigh a few thousand solar masses. But so far there have only been two tentative observations of objects of this sort.
In the past two years, scientists have succeeded in numerically simulating black hole mergers that incorporate Einstein's theory of relativity. One of the big surprises to come from this effort is the prediction that when two black holes that are rotating at different speeds or are different sizes combine, the newly merged black hole receives a big kick due to conservation of momentum, pushing it away in an arbitrary direction at velocities as high as 4,000 kilometers per second.
"This is much higher than anyone predicted. Even the average kick velocity of 200 kilometers per second is extremely high when compared to the escape velocities of typical astronomical objects," says Holley-Bockelmann. "We realized that basically any black hole merger would kick the new remnant out of a globular cluster, because the escape velocity is less than 100 kilometers per second."
Using the facilities of Vanderbilt's Advanced Center for Computation, Research and Education, Holley-Bockelmann's team ran a number of simulations of the growth of intermediate mass black holes as they combine with a number of stellar-sized black holes, which are plentiful in globular clusters, paying close attention to the kick they received after each merger.
"We used different assumptions for the initial black hole mass, for the range of stellar black hole masses within a globular cluster, and assumed that the spins and spin orientations were distributed randomly. With our most conservative assumptions, we found that, even if every globular cluster started out with an intermediate-sized black hole, only about 30 percent retain them through the merger epoch. With our least conservative assumptions, less than 2 percent of the globular clusters should contain intermediate mass black holes today," she says.
If the roughly 200 globular clusters in the Milky Way have indeed spawned intermediate-sized black holes, this means that hundreds of them are probably wandering invisibly around the Milky Way, waiting to engulf the nebulae, stars and planets that are unfortunate enough to cross their paths.
Fortunately, the existence of a few rogue black holes in the neighborhood does not present a major danger. "These rogue black holes are extremely unlikely to do any damage to us in the lifetime of the universe," Holley-Bockelmann stresses. "Their danger zone, the Schwarzschild radius, is really tiny, only a few hundred kilometers. There are far more dangerous things in our neighborhood!"
Vanderbilt University
Black Hole Current Events and Black Hole News RSSSwift XMM-Newton Satellites Tune Into a Middleweight Black Hole
While astronomers have studied lightweight and heavyweight black holes for decades, the evidence for black holes with intermediate masses has been much harder to come by.
New vista of Milky Way center unveiled
A dramatic new vista of the center of the Milky Way galaxy from NASA's Chandra X-ray Observatory exposes new levels of the complexity and intrigue in the Galactic center.
Invading black holes explain cosmic flashes
Black holes are invading stars, providing a radical explanation to bright flashes in the universe that are one of the biggest mysteries in astronomy today.
Sophisticated telescope camera debuts with peek at nest of black holes
Less than two months after they inaugurated the world's largest telescope, University of Florida astronomers have used one of the world's most advanced telescopic instruments to gather images of the heavens.
NGC 4945: The Milky Way's not-so-distant Cousin
ESO has released a striking new image of a nearby galaxy that many astronomers think closely resembles our own Milky Way.
First Black Holes Born Starving
The first black holes in the universe had dramatic effects on their surroundings despite the fact that they were small and grew very slowly, according to recent supercomputer simulations carried out by astrophysicists Marcelo Alvarez and Tom Abel of the Kavli Institute for Particle Astrophysics and Cosmology, jointly located at the Department of Energy's SLAC National Accelerator Laboratory and Stanford University, and John Wise, formerly of KIPAC and now of NASA Goddard Space Flight Center.
First black holes kept to a strict diet, study shows
A new supercomputer simulation designed to track the fate of the universe's first black holes finds that, counter to expectations, they couldn't efficiently gorge themselves on nearby gas.
Goddard-Led GEMS Mission to Explore the Polarized Universe
An exciting new astrophysics mission led by NASA's Goddard Space Flight Center in Greenbelt, Md., will provide a revolutionary window into the universe. Named the Gravity and Extreme Magnetism Small Explorer (GEMS), the satellite will be the first to systematically measure the polarization of cosmic X-ray sources.
Turbulence responsible for black holes' balancing act
We live in a hierarchical Universe where small structures join into larger ones. Earth is a planet in our Solar System, the Solar System resides in the Milky Way Galaxy, and galaxies combine into groups and clusters.
NASA's Fermi Finds Gamma-ray Galaxy Surprises
Back in June 1991, just before the launch of NASA's Compton Gamma-Ray Observatory, astronomers knew of gamma rays from exactly one galaxy beyond our own.
More Black Hole Current Events and Black Hole News Articles
 |
Black Hole by Charles Burns (Author) Winner of the Eisner, Harvey, and Ignatz Awards The setting: suburban Seattle, the mid-1970s. We learn from the outset that a strange plague has descended upon the area’s teenagers, transmitted by sexual contact. The disease is manifested in any number of ways — from the hideously grotesque to the subtle (and concealable) — but once you’ve got it, that’s it. There’s no turning back. As we inhabit the heads of several key characters — some kids who have it, some who don’t, some who are about to get it — what unfolds isn’t the expected battle to fight the plague, or bring heightened awareness to it , or even to treat it. What we become witness to instead is a fascinating and eerie portrait of the nature of high school alienation itself — the savagery,... |
 |
The Black Hole Starring: Ernest Borgnine, Joseph Bottoms, Robert Forster, Roddy McDowall, Tommy McLoughlin Also With: Anthony Perkins (Primary Contributor), Maximilian Schell (Primary Contributor) THE CREW OF THE SPACESHIP PALAMINO STUMBLES ACROSS THE LOST SHIP USS CYGNUS HOVERING ON THE EDGE OF AN IMMENSE BLACK HOLE. ONCE ABOARD THEY FIND THE SHIP IS MANNED BY ROBOTS ITS ONLY HUMAN INHABITANT ONE DR HANS REINHARDT AN EMINENT SCIENTIST MISSING FOR THE PAST TWENTY YEARS. |
 |
Death by Black Hole: And Other Cosmic Quandaries by Neil deGrasse Tyson (Author) “One of today’s best popularizers of science.”—Kirkus Reviews Loyal readers of the monthly “Universe” essays in Natural History magazine have long recognized Neil deGrasse Tyson’s talent for guiding them through the mysteries of the cosmos with stunning clarity and childlike enthusiasm. Here Tyson compiles his favorite essays across a myriad of cosmic topics. The title essay introduces readers to the physics of black holes by explaining just what would happen to your body if you fell into one, while “Hollywood Nights” assails Hollywood’s feeble efforts to get its night skies right. Tyson is the world’s ... |
 |
The Black Hole War: My Battle with Stephen Hawking to Make the World Safe for Quantum Mechanics by Leonard Susskind (Author) At the beginning of the 21st century, physics is being driven to very unfamiliar territory--the domain of the incredibly small and the incredibly heavy. The new world is a world in which both quantum mechanics and gravity are equally important. But mysteries remain. One of the biggest involved black holes. Famed physicist Stephen Hawking claimed that anything sucked in a black hole was lost forever. For three decades, Leonard Susskind and Hawking clashed over the answer to this problem. Finally, in 2004, Hawking conceded. THE BLACK HOLE WAR will explain the mind-blowing science that finally won out, and the emergence of a new paradigm that argues the world--this catalog, your home, your breakfast, you--is actually a hologram projected from the edges of... |
 |
The Black Hole Starring: Kristy Swanson; Judd Nelson; David Selby; Heather Dawn; Robert Giardina; Jennifer Lyn Quackenbush; Christa Campbell; Julia Sinks; Peter Mayer; James Anthony; Kevin Beyer; Dan Buran; Tim Snay; Adrian Rice; Greg Carr; Chris Nolte; Rick Tamblyn; Ermal Williamson; Rod Bernsen; Susan Wood Directed By: Tibor Takács A high-voltage sci-fi thriller loaded with explosive battles and gripping special effects. DVD Features include: Exploring The Black Hole: A Behind the Scenes Featurette with the Cast and Crew. |
 |
Black Holes: And Other Bizarre Space Objects (Science Frontiers) by David Jefferis (Author) |
 |
Exploring Black Holes: Introduction to General Relativity by Edwin F. Taylor (Author), John Archibald Wheeler (Author) Makes a quick, directed thrust through general relativity and black holes. Brings preliminary insights concerning the history and structure of the Cosmos. DLC: General relativity (Physics) |
 |
National Geographic: Monster Black Holes Starring: Michael Carroll Travel to the edge of space and beyond to discover natures ultimate abyss black holes. Explore where they are found, how they begin, and how it may be possible to harness and use the power they produce. In Monster Black Holes, scientists steadily piece together the complex dynamics of a black holes birth and are also examine the growth of a select few black holes to super massive proportions that dominate the centers of galaxies. As a monster black hole swallows everything in its path, it generates energy that shapes the universe around it in powerful ways. Journey into the heart of a black hole and explore what happens to matter when it falls into a black hole, and whether the Milky Way galaxy will one day come to an end when the black hole at the galaxys center explodes. |
 |
Black Holes and Time Warps: Einstein's Outrageous Legacy (Commonwealth Fund Book Program) by Kip S. Thorne (Author), Stephen Hawking (Foreword) In this masterfully written and brilliantly informed work, Dr. Thorne, the Feynman Professor of Theoretical Physics at Caltech, leads readers through an elegant, always human, tapestry of interlocking themes, answering the great question: what principles control our universe and why do physicists think they know what they know? Features an introduction by Stephen Hawking. |
 |
The Black Hole (Original Motion Picture Soundtrack) Composed and conducted by John Barry (Performer) This is the 1979 Original Motion Picture Soundtrack of "The Black Hole", With music composed and conducted by John Barry. A digital recording, this Buena Vista record number 5008 (from Walt Disney Productions) was produced by John Barry and Engineered by Danny Wallin. The Black Hole motion picture starred Maximillian Schell, Anthony Perkins, Robert Forster, Joseph Bottoms, Yvette Mimieux and Ernest Borgnine. The movie was produced by Ron Miller and directed by Gary Nelson. The screenplay was by Jeb Rosebrook and Gerry Day from a story by Jeb Rosebrook and Bob Barbash & Richard Landau. |
| © 2009 BrightSurf.com |