Black hole simulations on XSEDE supercomputers present new view of jets and accretion disks

Feb 21, 2013
3D snapshot for an evolved Black Hole (BH) model. The disk and jet near the BH are aligned with the BH spin axis and point mostly in and out of the figure plane, whereas at larger distances the jet points roughly halfway between the BH spin axis and the disk's rotational axis (pointing along the orange cylinder). Credit: Supported by NASA, the Princeton Center for Theoretical Science and NSF Extreme Science and Engineering Discovery Environment (XSEDE).

Voracious absences at the center of galaxies, black holes shape the growth and death of the stars around them through their powerful gravitational pull and explosive ejections of energy.

"Over its lifetime, a black hole can release more energy than all the stars in a galaxy combined," said Roger Blandford, director of the Kavli Institute for and Cosmology and a member of the U.S. . " have a major impact on the and the environmental growth and evolution of those galaxies."

grow so strong close to a black hole that even light cannot escape from within, hence the difficulty in observing them directly. Scientists infer facts about black holes by their influence on the around them: the orbit of stars and clumps of detectable energy.

With this information in hand, scientists create computer models to understand the data and to make predictions about the physics of distant regions of space. However, models are only as good as their assumptions.

"All tests of general relativity in the weak limit, like in our solar system, fall directly along the lines of what Einstein predicted," explained Jonathan McKinney, an assistant professor of physics at the University of Maryland at College Park. "But there is another regime—which has yet to be tested, and which is the hardest to test—that represents the strong limit. And according to Einstein, gravity is strongest near black holes."

This makes black holes the ultimate experimental testing grounds for Einstein's .

While black holes cannot be observed, they are typically accompanied by other objects with distinctive features that can be seen, including , which are circling disks of superhot matter on our side of the black hole's ""; and , high-powered streams of ionized gases that shoot hundreds of thousands of light years across the sky.

In a paper published in Science in January 2013, McKinney, Tchekhovskoy and Blandford predicted the formation of accretion disks and relativistic jets that warp and bend more than previously thought, shaped both by the extreme gravity of the black hole and by powerful magnetic forces generated by its spin. Their highly detailed models of the black hole environment contribute new knowledge to the field.

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For decades, a simplistic view of the accretion disks and polar jets reigned. It was widely believed that accretion disks sat like flat plates along the outer edges of black holes and that jets shot straight out perpendicularly. However, new 3D simulations performed on the powerful supercomputers of the National Science Foundation's Extreme Science and Engineering Discovery Environment (XSEDE) and NASA overturned this oversimplified view of jets and disks.

The simulations show that the jet is aligned with the black hole's spin near the black hole but that it gradually gets pushed by the disk material and becomes parallel to (but offset from) the disk's rotational axis at large distances. The interaction between the jet and disk leaves a warp in the accretion disk density.

"An important aspect that determines jet properties is the strength of the magnetic field threading the black hole," said Alexander Tchekhovskoy, a post-doctoral fellow at the Princeton Center for Theoretical Science. "While in previous works it was a free parameter, in our series of works the field is maximum: it is as strong as a black hole's gravity pull on the disk."

In the simulations, the twisting energy grows so strong that it actually powers the jet. In fact, the jet can reorient the accretion disk, rather than the other way around, as was thought previously.

"People had thought that the disk was the dominant aspect," McKinney said. "It was the dog and the jet was the wagging tail. But we found that the magnetic field builds up to become stronger than gravity, and then the jet becomes the dog and the disk becomes the wagging tail. Or, one can say the dog is chasing its own tail, because the disk and jet are quite balanced, with the disk following the jet—it's the inverse situation to what people thought."

What does this have to do with Einstein and his theory of general relativity?

Astronomers are closer than ever to being able to see the details of the jets and accretion disks around black holes. In a September 2012 paper in Science, Sheperd Doeleman of MIT reported the first images of the jet-launching structure near the supermassive black hole, M87, at the center of a neighboring galaxy, captured using the Event Horizon Telescope, a very long baseline interferometry (VLBI) array composed of four telescopes at three geographical locations. It constituted a small sliver of a vast skyscape, yet the results give astronomers like McKinney, Tchekhovskoy and Blandford the hope that they will get their first comprehensive glimpse into the black hole's neighborhood in the next three to five years.

"We'll see the gases swirl around the black hole and other optical effects that will be signatures of a black holes in spacetime that one can look out for," said Blandford.

The observations will either match models like theirs, or they will be different. Both outcomes will tell researchers a lot.

"If you don't have an accurate model and anything can happen as far as you understand, then you're not going to be able to make any constraints and prove one way or another whether Einstein was right," McKinney explained. "But if you have an accurate model using Einstein's equations, and you observe a black hole that is very different from what you expected, then you can begin to say that he may be wrong."

The model Blandford and others generated using supercomputing simulations will help serve that comparative role. But they need to add one crucial element to make the simulations meaningful: a way of translating the physics of the black hole system into a visual signal as it would be seen from the vantage point of our telescopes, billions of light years away.

"We're in the process of making our simulations shine, so they can be compared with observations," McKinney said, "not only to test our ideas of how these disks and jets work, but ultimately to test general relativity."

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User comments : 21

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rubberman
1 / 5 (3) Feb 21, 2013
"Over its lifetime, a black hole can release more energy than all the stars in a galaxy combined," said Roger Blandford,- beginning of paragraph 1

"Gravitational forces grow so strong close to a black hole that even light cannot escape from within, hence the difficulty in observing them directly."- beginning of paragraph 2

Which is it? If one of these is true, they both can't be.
Q-Star
4.2 / 5 (5) Feb 21, 2013
"Over its lifetime, a black hole can release more energy than all the stars in a galaxy combined," said Roger Blandford,- beginning of paragraph 1

"Gravitational forces grow so strong close to a black hole that even light cannot escape from within, hence the difficulty in observing them directly."- beginning of paragraph 2

Which is it? If one of these is true, they both can't be.


The energy released (first reference) is not from within the event horizon,,,, it is the energy concentrated and then ejected in, around and from the accretion disk.

The second reference you make is true for what falls within the event horizon.

No contradiction, two different places. Quite clearly stated in paragraph six through seven
.
rubberman
1 / 5 (1) Feb 21, 2013
Ahhh, so the first paragraph should have been worded that it can accelerate more accreted energy away, as opposed to actually releasing it...
Q-Star
4 / 5 (4) Feb 21, 2013
Ahhh, so the first paragraph should have been worded that it can accelerate more accreted energy away, as opposed to actually releasing it...


When reading a short article like this one, it's easy to form a question during the reading, but it is just as easy to finish the article to see if your question is answered. And most of the time, finishing the article is easier than asking your question.

It's a science article, brief and concise, not an essay to demonstrate perfect writing skills. That's why there were a few more paragraphs to follow the first two, to pass on just what the researchers were studying and how.

But to the actual article, I'm pleased to see models expanded upon to reflect more detailed descriptions of observations, it shows progress in our understanding. There are so many data points we have at our disposal that we need bigger and faster computers to use them effectively.

rubberman
1 / 5 (1) Feb 21, 2013
"That's why there were a few more paragraphs to follow the first two, to pass on just what the researchers were studying and how."

I did read the article, they are studying a simulation that as of yet has no way of being validated as accurate.

"It's a science article, brief and concise, not an essay to demonstrate perfect writing skills."

Being concise while writing an article requires good writing skills...maybe not perfect. Let's ask some other physicists what else black holes "release".....
Q-Star
4 / 5 (4) Feb 21, 2013
they are studying a simulation that as of yet has no way of being validated as accurate


Not so. In doing these simulations, you begin with an "idea", a concept of what may be happening with things observed. Then you program for various parameters which may influence the outcome. Since there is absolutely no way to include ALL available data, and ALL available parameters, you include as many as your computer and computer time allow.

After doing that, the simulation is quickly validated or assessed for accuracy. By comparing it with actual observations. These simulations are done not to predict, but done to see if your theories in fact lead to what you are actually observing.

The entire purpose of this kind of simulation, to see if what you are observing jibes with how you think it working. The closer the simulation matches your previous observations, the closer you were in positing the "how". When the simulations fail to match your observations, then you rethink "how".
cantdrive85
1 / 5 (4) Feb 21, 2013
"An important aspect that determines jet properties is the strength of the magnetic field threading the black hole," said Alexander Tchekhovskoy, a post-doctoral fellow at the Princeton Center for Theoretical Science. "While in previous works it was a free parameter, in our series of works the field is maximum: it is as strong as a black hole's gravity pull on the disk."


"Free parameter" is code for we have absolutely no idea what we are doing, it's as if throwing darts at a dart board was used to program the assumptions. BTW, It was my understanding that the gravitational forces of a black hole was the most powerful force in the universe. What observation or data gave them "scientific licence" to arbitrarily assume a force which is up to 42 orders of magnitude stronger than gravity to be equivalent to gravity? Garbage in, garbage out!
rubberman
1 / 5 (1) Feb 21, 2013
they are studying a simulation that as of yet has no way of being validated as accurate


Not so. In doing these simulations, you begin with an "idea"..


"the results give astronomers like McKinney, Tchekhovskoy and Blandford the hope that they will get their first comprehensive glimpse into the black hole's neighborhood in the next three to five years.

"We'll see the gases swirl around the black hole and other optical effects that will be signatures of a black holes in spacetime that one can look out for," said Blandford.

The observations will either match models like theirs, or they will be different. Both outcomes will tell researchers a lot."

I would say it is so...they say it is so.

Tausch
1 / 5 (2) Feb 21, 2013
Fives. For mutual discourse. Rubber for standing in for readers susceptible to a similar understandings. Q-star for dispelling understandings that short change consistency.
If you want, I'll post the ratings I spout.
Your call.
Q-Star
3 / 5 (2) Feb 21, 2013
What observation or data gave them "scientific licence" to arbitrarily assume a force which is up to 42 orders of magnitude stronger than gravity to be equivalent to gravity? Garbage in, garbage out!


Who ever said that that gravity was equivalent to the electromagnetic force? Not me, all I have said is they do different things. If they didn't do what they do, the things we observe would be different.

Observing the moon circling the Earth? The Earth orbiting the Sun? The lump on your head when you fell down the stairs? We can list observations of gravity in action until 10^42 volumes of lists are compiled.

By the By: Having any luck finding an astrophysics text in common use today that completely ignores plasma and electromagnetics? I didn't think so,,, but keep searching. Maybe you will actually learn something about that so-called "standard model" you keep referring to. Is the "gravity is equal" to be found in one of those textbooks also? Show me.
Q-Star
4 / 5 (4) Feb 21, 2013
The observations will either match models like theirs, or they will be different. Both outcomes will tell researchers a lot."


Exactly as I said. The simulation is compared to observations. Your "hows" are either on target, or you need to rethink your "hows".

In this area of science, observing over two years, is like a blink of the eye. It's almost instantaneous. Another shortcoming in how the article and I express the functioning of the routine science in this discipline.
radek
1 / 5 (2) Feb 21, 2013
"Over its lifetime, a black hole can release more energy than all the stars in a galaxy combined," said Roger Blandford,-


I would add

"But we found that the magnetic field builds up to become stronger than gravity, and then the jet becomes the dog and the disk becomes the wagging tail."

"McKinney said, "not only to test our ideas of how these disks and jets work, but ultimately to test general relativity."

for me it`s a model but looks like thay want to challange GR.
I mentioned few times that BH are the keys to understand Universe.
I won`t be suprised if observations confirm that BH are the sources of all existing matter by jets mechanism (i.e. is possible to escape event horizon like Hawking radiation do).

cantdrive85
1 / 5 (4) Feb 21, 2013
Q- Who ever said that that gravity was equivalent to the electromagnetic force?


It's in the article...

"the field is maximum: it is as strong as a black hole's gravity pull on the disk."

"People had thought that the disk was the dominant aspect," McKinney said. "It was the dog and the jet was the wagging tail. But we found that the magnetic field builds up to become stronger than gravity, and then the jet becomes the dog and the disk becomes the wagging tail. Or, one can say the dog is chasing its own tail, because the disk and jet are quite balanced, with the disk following the jet—it's the inverse situation to what people thought."


What they are describing is two interacting birkeland currents, just as the particle-in-cell simulations have shown.
http://public.lan...lsen.pdf
eachus
1 / 5 (1) Feb 23, 2013
It's in the article...

"the field is maximum: it is as strong as a black hole's gravity pull on the disk."


If the (EM) force is stronger, then matter leaves the accretion disk. What if the magnetic field is weaker? The (ionized) matter in the disk will fall inward until they balance at the outer edge. If you actually watched the simulation, you could see the disk material getting blown away from time to time.

Anyway, the simulation started with a nice quiet model, and it evolved to the sort of twisted jets seen around actual SMBHs. (Resolving an accretion disk is currently not possible, but should be when the blob of gas near SagA* gets there this year. We will have an active SMBH about as close to Earth as you would want.)
rubberman
1 / 5 (1) Feb 25, 2013
"In doing these simulations, you begin with an "idea", a concept of what may be happening with things observed."

"Exactly as I said. The simulation is compared to observations. Your "hows" are either on target, or you need to rethink your "hows"."

Q - I linked a video that met the above criteria regarding photonic properties that you described as "art", not science. I don't see a difference....
Q-Star
3.7 / 5 (3) Feb 25, 2013
Q - I linked a video that met the above criteria regarding photonic properties that you described as "art", not science. I don't see a difference....


The video, used an "artist's" visualization of what he "pictured" happening in his "imagination".

A computer simulation like this one uses observed data, along with various physical formulas and processes to try to match something "seen" to a process.

The video is created with a conclusion in mind. The simulation starts with a process in mind to see if it will end up with the "conclusion" after running.

That's basically the difference.
rubberman
1 / 5 (1) Feb 25, 2013
Actually the video I linked was made by a plasma physicist who, on the strength of the first 3 of his 6 part set has been approached by Nasa with regards to deep space propulsion and by three labs in the field of photonics simply thanking him for opening their eyes as to why they (photons) behave how they do.
He understands more about magnetics/energy and EM than you are willing to credit him for by referring to him as an artist.

THIS simulation is based on an unobservable entity and "assumed" characterisitcs (various physical formulas) applied by US, formulas we THINK apply to what MAY be happening in this region we can't observe, based on what we actually do observe in the regions we can. I did't even dispute the accuracy of this simulation, just the wording of the text at the beginning. But from a strictly factual standpoint, this is more "art" than what you described as art.
Q-Star
3 / 5 (2) Feb 25, 2013
Actually the video I linked was made by a plasma physicist who, on the strength of the first 3 of his 6 part set has been approached by Nasa with regards to deep space propulsion and by three labs in the field of photonics simply thanking him for opening their eyes as to why they (photons) behave how they do.


Bold claim, or bold claim of acclamation. First time I've ever heard NASA and Labs getting their science from youtube,,, they usually get their their eye-opening science from the universities, journals, and established entities,,,,

NASA scientists scooped and schooled by youtube, who would have thunk it? Bold claim, just a tad over the top don't ya think?
rubberman
1 / 5 (1) Feb 25, 2013
Bold indeed. And i only have the maker of the video's word (which I choose to trust) to rely upon. So it is even more tenuous viewed from that perspective.

As far as being an established entity goes, his work (7 years worth, which I have seen some of) that isn't on Youtube is convincing to put it mildly, and with sound evidence to it's accuracy warrants further investigation by people educated in the various fields it covers. The astrophysics work came after the atomic structure work....so he did start out small and work his way up. He just neglected particle physics and went right to the properties of energy/magnetism. Nobody educated at a university would've approached it in his way, or published it as it isn't in line with established views on the subject.

Believe me if at the end of the day it's "not even wrong" I'll issue a formal apology to you for insulting your education. Otherwise I'll just point out the work when it goes public.
Q-Star
3 / 5 (2) Feb 25, 2013
Believe me if at the end of the day it's "not even wrong" I'll issue a formal apology to you for insulting your education. Otherwise I'll just point out the work when it goes public.


You shouldn't issue an apology to anyone. So far as I've seen, you've always been thoughtful and sincere. You certainly haven't insulted me.

I'm jaded I so suppose because in the course of doing what I do, I run into hundreds or thousands of people on the internet, each of them have found THE fundamental TRUTH that all others have missed.

Everything from: "There is no such thing as gravity" to "electron ducks paddling on transverse longitudinal waves in the aether" to "gravity is inconsequential because everything is plasma" to "God did it".

Very smart people use very expensive toys to explore the wonders of nature, entire systems of people and machines. People who have dedicated a significant portion of their lives preparing themselves to explore the questions.

Will Continue,,,,,,
Q-Star
1 / 5 (1) Feb 25, 2013
Every scientist's greatest distraction is all the hundreds of people who send them "ideas", "a new approach", "a new way of looking at",,,, when many smart people have already tested or thought of it and found it to be impractical or a nonstarter.

Every scientist lives for the day he might discover the next revolutionary idea, they live for the day that they find the thing which will cause a law, a theory, a satellite or professorship named after them.

They don't hold on the to old because it is safe, or lucrative, or "mainstream",,,, they hold on to things which work, and cast aside or adjust the things that don't work.

We have reached the point where NEW science must be accompanied by extraordinary confirmation, in the mathematical proofs and theoretical models. It costs to much to test every "wild idea" that comes along, especially when it comes along without a firm predictive foundation. The science dollars are to short as it is.