|
No matter their size black holes 'feed' in the same way
December 07, 2006Research by UK astronomers, published today in Nature (7th December 2006) reveals that the processes at work in black holes of all sizes are the same and that supermassive black holes are simply scaled up versions of small Galactic black holes.
For many years astronomers have been trying to understand the similarities between stellar-mass sized Galactic black hole systems and the supermassive black holes in active galactic nuclei (AGN).In particular, do they vary fundamentally in the same way, but perhaps with any characteristic timescales being scaled up in proportion to the mass of the black hole. If so, the researchers proposed, we could determine how AGN should behave on cosmological timescales by studying the brighter and much faster galactic systems.
Professor Ian McHardy, from the University of Southampton, heads up the research team whose findings are published today (along with colleagues Drs Elmar Koerding and Christian Knigge and Professor Rob Fender, and Dr Phil Uttley, currently working at the University of Amsterdam). Their observations were made using data from NASA�s Rossi X-ray Timing Explorer and XMM Newton�s X-ray Observatory.
Professor McHardy comments, "By studying the way in which the X-ray emission from black hole systems varies, we found that the accretion or �feeding� process-where the black hole is pulling in material from its surroundings-is the same in black holes of all sizes and that AGN are just scaled-up Galactic black holes. We also found that the way in which the X-ray emission varies is strongly correlated with the width of optical emission lines from black hole systems."
He adds, "These observations have important implications for our understanding of the different types of AGN, as classified by the width of their emission lines. Thus narrow line Seyfert galaxies, which are often discussed as being unusual, are no different to other AGN; they just have a smaller ratio of mass to accretion rate."
The research shows that the characteristic timescale changes linearly with black hole mass, but inversely with the accretion rate (when measured relative to the maximum possible accretion rate). This result means that the accretion process is the same in black holes of all sizes. By measuring the characteristic timescale and the accretion rate, the team argues this simple relationship can help determine black hole masses where other methods are very difficult, for example in obscured AGN or in the much sought after intermediate mass black holes.
Professor McHardy continues: "Accretion of matter into a black hole produces strong X-ray emission from very close to the black hole itself. So, studying the way in which the X-ray emission varies with time, known as the X-ray lightcurves, provides one of the best ways of understanding the behaviour of black holes.
It has been known for over two decades that characteristic timescales can be seen in the X-ray lightcurves of Galactic black hole systems. The timescales are short (second) and so can be found in short observations. However to find the equivalent timescales in AGN is much harder as we must observe for months or years."
Particle Physics & Astronomy Research Council
Professor McHardy comments, "By studying the way in which the X-ray emission from black hole systems varies, we found that the accretion or �feeding� process-where the black hole is pulling in material from its surroundings-is the same in black holes of all sizes and that AGN are just scaled-up Galactic black holes. We also found that the way in which the X-ray emission varies is strongly correlated with the width of optical emission lines from black hole systems."
He adds, "These observations have important implications for our understanding of the different types of AGN, as classified by the width of their emission lines. Thus narrow line Seyfert galaxies, which are often discussed as being unusual, are no different to other AGN; they just have a smaller ratio of mass to accretion rate."
The research shows that the characteristic timescale changes linearly with black hole mass, but inversely with the accretion rate (when measured relative to the maximum possible accretion rate). This result means that the accretion process is the same in black holes of all sizes. By measuring the characteristic timescale and the accretion rate, the team argues this simple relationship can help determine black hole masses where other methods are very difficult, for example in obscured AGN or in the much sought after intermediate mass black holes.
Professor McHardy continues: "Accretion of matter into a black hole produces strong X-ray emission from very close to the black hole itself. So, studying the way in which the X-ray emission varies with time, known as the X-ray lightcurves, provides one of the best ways of understanding the behaviour of black holes.
It has been known for over two decades that characteristic timescales can be seen in the X-ray lightcurves of Galactic black hole systems. The timescales are short (second) and so can be found in short observations. However to find the equivalent timescales in AGN is much harder as we must observe for months or years."
Particle Physics & Astronomy Research Council
Black Holes News and Current Black Holes Events RSSUCSB professor's paper on safety of large hadron collider to be published in Physical Review D
Particle colliders creating black holes that could devour the Earth. Sounds like a great Hollywood script.
Radio Telescopes Reveal Unseen Galactic Cannibalism
Radio-telescope images have revealed previously-unseen galactic cannibalism -- a triggering event that leads to feeding frenzies by gigantic black holes at the cores of galaxies. Astronomers have long suspected that the extra-bright cores of spiral galaxies called Seyfert galaxies are powered by supermassive black holes consuming material. However, they could not see how the material is started on its journey toward the black hole.
Black holes have simple feeding habits
The biggest black holes may feed just like the smallest ones, according to data from NASA's Chandra X-ray Observatory and ground-based telescopes. This discovery supports the implication of Einstein's relativity theory that black holes of all sizes have similar properties, and will be useful for predicting the properties of a conjectured new class of black holes.
UC Santa Cruz physicists eagerly await launch of NASA space telescope they helped build
When NASA launches its newest space observatory, physicists at the University of California, Santa Cruz, will be watching as the product of nearly 16 years of hard work blasts into orbit.
CSI: Milky Way team works scene of dead star
Like a team of forensic detectives in a television show that could be called "CSI: Milky Way," a University of Chicago astrophysicist and his associates are piecing together how a mysterious infrared ring got left around a dead star that displays a magnetic field trillions of times more intense than Earth's.
Supernova birth seen for first time
Astronomers have seen the aftermath of spectacular stellar explosions known as supernovae before, but until now no one has witnessed a star dying in real time.
The Mouse That Roared: Pipsqueak Star Unleashes Monster Flare
On April 25, NASA's Swift satellite picked up the brightest flare ever seen from a normal star other than our Sun. The flare, an explosive release of energy from a star, packed the power of thousands of solar flares. It would have been visible to the naked eye if the star had been easily observable in the night sky at the time.
Searching the heavens
A new space mission, due to launch this month, is going to shed light on some of the most extreme astrophysical processes in nature - including pulsars, remnants of supernovae, and supermassive black holes.
Catching a Glimpse of a Black Hole's Fury
Using the National Science Foundation's (NSF) Very Long Baseline Array (VLBA) and a host of international telescope partners, a team of researchers has made the clearest observation yet of innermost region of a black hole.
Galaxies gone wild!
Interacting galaxies are found throughout the Universe, sometimes as dramatic collisions that trigger bursts of star formation, on other occasions as stealthy mergers that result in new galaxies.
More Black Holes News Articles
 | Death by Black Hole: And Other Cosmic Quandaries by Neil deGrasse Tyson |
 | The Black Hole War: My Battle with Stephen Hawking to Make the World Safe for Quantum Mechanics by Leonard Susskind |
 | Black Hole by Charles Burns |
 | Radical Amazement: Contemplative Lessons from Black Holes, Supernovas, And Other Wonders of the Universe by Judy Cannato |
 | Black Holes and Time Warps: Einstein's Outrageous Legacy (Commonwealth Fund Book Program) by Kip S. Thorne |
 | An Introduction To Black Holes, Information And The String Theory Revolution: The Holographic Universe by Leonard Susskind, James Lindesay |
 | A Brief History of Time: From the Big Bang to Black Holes by Stephen W. Hawking |
 | Geons, Black Holes, and Quantum Foam: A Life in Physics by John Archibald Wheeler, Kenneth W. Ford, Kenneth Ford |
 | Cosmic Catastrophes: Exploding Stars, Black Holes, and Mapping the Universe by J. Craig Wheeler |
 | A Brief History of Time: From the Big Bang to Black Holes by Stephen W. Hawking |
| © 2008 BrightSurf.com |