Magnetic Fields Shape the Jets Pouring Out of Supermassive Black Holes (with video)
Written by Fraser Cain
The cores of galaxies contain supermassive black holes, containing hundreds of millions of times the mass of Sun. As matter falls in, it chokes up, forming a super hot accretion disk around the black hole. From this extreme environment, the black hole-powered region spews out powerful jets of particles moving at the speed of light. Astronomers have recently gotten one of the best views at the innermost portion of the jet.
A team of astronomers led by Alan Marscher, of Boston University, used the National Radio Astronomy Observatory's Very Long Baseline Array (VLBA) to peer at the central region of a galaxy called BL Lacertae.
"We have gotten the clearest look yet at the innermost portion of the jet, where the particles actually are accelerated, and everything we see supports the idea that twisted, coiled magnetic fields are propelling the material outward," said Alan Marscher, of Boston University, leader of an international research team. "This is a major advance in our understanding of a remarkable process that occurs throughout the Universe," he added.
Here's how the theory goes. As material falls into the supermassive black hole faster than it can consume it, an accretion disk forms. This is a flattened, rotating disk that circles the black hole. The spinning interaction with the black hole creates powerful magnetic fields that twist and form into a tightly-coiled bundle. It's these magnetic fields that blast out particles into focused beams.
The theorists expected that the region inside the acceleration region would follow a corkscrew-shaped path inside the twisting magnetic fields. Furthermore, researchers expected that light and material would brighten when it was pointed directly towards Earth. And finally, the astronomers expected that there should be a flare when material hits a stationary shock wave called the "core" after it comes out of the acceleration region.
And that's just what the observations show. The VLBA was used to study how a knot of material was ejected out of the black hole's environment. As the knot moved through the stationary shock wave, it flared just as the theorists had predicted.
Original Source: NRAO News Release
Filed under: Black Holes
April 24th, 2008 at 1:31 am
….beautiful
April 24th, 2008 at 5:17 am
You stated, "From this extreme environment, the black hole-powered region spews out powerful jets of particles moving at the speed of light." I don't understand - if nothing, not even light can escape a black hole, how does one explain this observation?
April 24th, 2008 at 5:58 am
The material is forced out before it reaches the event horizon. Once material goes past the event horizon, there is no escape.
April 24th, 2008 at 6:15 am
"…at the speed of light…" Really? So, does the magnetic fields have the energy of all the universe? Is Einstein wrong about the amount of energy needed to move matter at the speed of light? Let me know because I have an idea for rapid trasnit that will make me a billion-aire. Maybe it really doesn't eject in-falling matter "at the speed of light." Perhaps 99.99% of the speed - maybe.
April 24th, 2008 at 6:44 am
Whats the difference between mass and size. When they say it has the mass of 1 million suns but is only the size of earth that confuses me.
April 24th, 2008 at 8:43 am
Hi LLDIAZ,
Size and mass are different quantities, but the difference can be intuitively confusing, as we tend to naturally use the size of an object as an indicator of it's mass quite naturally here on Earth.
Size is the physical extent of an object. You can describe it with more specific terms such as width, height, thickness, volume etc. Size is a bit of a general term.
Mass is the measure of how much matter an object contains. Intuitively, a heavier object contains more mass that a lighter object, etc. It is measured in Kilograms in the metric system.
The two quantities are related by density. A large object containing not much mass is regarded as relatively less dense (such as a balloon filled with air) than an object that is smaller and contains more mass (such as a block of lead).
And so we come to black holes - these are the densest objects in the universe, containing many stars worth of material crammed into a very small space by a phenomenon known as gravitational collapse. Check out this article if you feel like reading further:
http://en.wikipedia.org/wiki/Black_hole
April 24th, 2008 at 8:44 am
Hmmm apologies if posted twice, computer tripping out? Frustrating!
April 24th, 2008 at 8:46 am
Nooooo! post lost twice!
Check out this article LLDIAZ, it may answer some of your questions:
http://en.wikipedia.org/wiki/Density
April 24th, 2008 at 8:47 am
Damn! Post lost twice! Check out wikipedia LLDIAZ. Look up mass and volume on there… I wrote a post but it doesn't seem to want to log it!
April 24th, 2008 at 11:05 am
It is possible if you think about it. The singularity itself is almost infinitely small. (The word infinite is important here) so we are dealing with an object that does have the power to prove E=mc^2. the jets that exit the "Hole" have already had incredible forces and energies in the mix. The theory is that matter is reduced to sub-atomic particles, and we believe that this occurs in the accretion disk. The energy released when you break a nuclear bond is huge. Throw in gravitational and magnetic forces on top of that, and it is plausible that this can and does occur. Einstein wasn't wrong, he just hasn't been proven "Right" enough yet.
April 25th, 2008 at 2:40 am
beautiful animation. Top one, people!
April 25th, 2008 at 2:55 am
I am unable to convince myself with the question how the accretion disk is formed. Whatever is written can be possible only for blackholes with some rotation. I dont know how, if possible, it makes any sense if the blackhole is not spinning and the disk is formed. If it is possible, somebody tell me how.
April 25th, 2008 at 6:23 am
Tajadar: I'm not 100% certain of this, but I think it been predicted that all black holes spin. In mathematical models, it's possible to have a non-rotating black hole, but in reality, they all rotate.
LLDIAZ: As for mass: Think of a lead bar that weighs 100 pounds. Then think of a pile of feathers that weighs 100 pounds. They both weigh the same, but the feather pile is much bigger. Same thing with a black hole. Black holes have a lot of mass in a small size.
April 25th, 2008 at 1:09 pm
gotcha !!
nice example!!
April 25th, 2008 at 1:09 pm
Accretion disks form because collisions between the particles making up a spherical cloud of gas or dust tend to average out their angular momentum. This causes the cloud to collapse into a disk, where the orbits of the particles don't cross, minimizing the number of collisions. The rotation of the primary also plays a role, tending to align the disk with its own equator (I haven't quite figured out the 'how' of that last part, yet. It's something to do with the oblateness of rotating bodies).
Also, the matter of the disk, as it falls into the black hole, transfers its angular momentum to the hole, which also helps to align the hole's equator with the accretion disk.