Surprisingly strong magnetic fields challenge black holes' pull

Jun 04, 2014
This is a computer simulation of gas (in yellow) falling into a black hole (too small to be seen). Twin jets are also shown with magnetic field lines. Credit: Alexander Tchekhovskoy, Berkeley Lab

A new study of supermassive black holes at the centers of galaxies has found magnetic fields play an impressive role in the systems' dynamics. In fact, in dozens of black holes surveyed, the magnetic field strength matched the force produced by the black holes' powerful gravitational pull, says a team of scientists from the U.S. Department of Energy's Lawrence Berkeley National Laboratory and Max Planck Institute for Radio Astronomy (MPIfR) in Bonn, Germany. The findings are published in this week's issue of Nature.

"This paper for the first time systematically measures the strength of magnetic fields near black holes," says Alexander Tchekhovskoy, the Berkeley Lab researcher who helped interpret the observational data within the context of existing computational models. "This is important because we had no idea, and now we have evidence from not just one, not just two, but from 76 black holes."

Previously, Tchekhovskoy, who is also a postdoctoral fellow at the University of California, Berkeley, had developed computational models of black holes that included magnetic fields. His models suggested a black hole could sustain a magnetic field that was as strong as its gravity, but there was not yet observational evidence to support this prediction. With the two forces balancing out, a cloud of gas caught on top of the magnetic field would be spared the pull of gravity and instead levitate in place.

The strength was confirmed by evidence from jets of gas that shoot away from . Formed by magnetic fields, these jets produce a radio emission. "We realized that the radio emission from black holes' jets can be used to measure the near the black hold itself," says Mohammad Zamaninasab, the lead author of the study, who did the work while at MPIfR.

Other research teams had previously collected radio-emission data from "radio-loud" galaxies using the Very Long Baseline Array, a vast network of radio telescopes in the United States. The researchers analyzed this pre-existing data to create maps at different wavelengths. Shifts in jet features between different maps let them calculate the field strength near the black hole.

Based on the results, the team found not only that the measured magnetic fields can be as strong as a black hole's gravity, but that they are also comparable in strength to those produced inside MRI machines found in hospitals—roughly 10,000 times greater than the field of the Earth itself.

Tchekhovskoy says the new results mean theorists must re-evaluate their understanding of black-hole behavior. "The magnetic fields are strong enough to dramatically alter how gas falls into and how gas produces outflows that we do observe, much stronger than what has usually been assumed," he says. "We need to go back and look at our models once again."

Explore further: Violent gamma-ray outbursts near supermassive black holes

More information: Paper: Dynamically important magnetic fields near accreting supermassive black holes, DOI: 10.1038/nature13399

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hemitite
5 / 5 (1) Jun 04, 2014
It would make sense that the strength of the magnetic field produced by the orbital motion and turbulence of the plasma accretion disk would be on the same order as that of the black hole's gravitational field. The kinetic energy produced by the latter leads to the generation of the former.
Protoplasmix
5 / 5 (1) Jun 05, 2014
It would make sense that the strength of the magnetic field produced by the orbital motion and turbulence of the plasma accretion disk would be on the same order as that of the black hole's gravitational field. The kinetic energy produced by the latter leads to the generation of the former.

Actually, the field inside the disk can be of arbitrary shape—it's a question of the shape of the field supporting the disk against the gravitational attraction. It's an evaluation of the stress tensor: per unit surface area of the disk it works out to be the product of the magnetic field strength radially outward times the field strength vertically in the disk, which has to counter the gravity: an integral of the mass density taken over the interval of the disk thickness (times a factor of 2-pi and Newton's g).

See: Fig. 2.4 on p. 55 of "Essential magnetohydrodynamics for astrophysics" at
http://de.arxiv.o...1.5572v1
cantdrive85
1.5 / 5 (8) Jun 05, 2014
"This is important because we had no idea...
"The magnetic fields are strong enough to dramatically alter how gas falls into black holes and how gas produces outflows that we do observe, much stronger than what has usually been assumed," he says. "We need to go back and look at our models once again."


No idea? Assumed?

Compare this image;
http://en.wikiped...rope.svg

to the image above...

Seems the Birkeland currents powering the plasmoid at the core of the galaxy are in plain view.

This is what the plasmoid looks like;
https://www.googl...imgdii=_
GuruShabu
1 / 5 (4) Jun 05, 2014
Halton Arp has already shown this 50 years ago.
antialias_physorg
3.7 / 5 (6) Jun 05, 2014
but that they are also comparable in strength to those produced inside MRI machines found in hospitals—roughly 10,000 times greater than the field of the Earth itself.

Field strength of Earth (at the surface) is 25-65 microtesla.
10000 times that would be 250 - 650 Tesla.
Most current MRI scanners operate WAY below that (at between 3-7 Tesla, with some experimental ones going to 11T).
antialias_physorg
4.2 / 5 (5) Jun 05, 2014
Ah..my bad...I screwed up micro and milli (Duh. Shouldn't post without double checking).
So the black hold field strength would be 0.25 to 0.65 Tesla (which is equilvalent to old MR machines)
Protoplasmix
5 / 5 (2) Jun 05, 2014
Compare this image;
http://en.wikiped...rope.svg
to the image above...

Hi, CD85 – the image in Fig. 2.5 on p. 57 (see link in my previous post) of a jet from a MHD simulation is much closer in appearance to the illustration above. Also, section 2.1 (p. 39-40) gives a derivation of Alven's theorem. What do think about that? Did you read it?
Protoplasmix
5 / 5 (2) Jun 05, 2014
late edit: Alven > Alfven
katesisco
1 / 5 (3) Jun 05, 2014
Previously, Tchekhovskoy, who is also a postdoctoral fellow at the University of California, Berkeley, had developed computational models of black holes that included magnetic fields. His models suggested a black hole could sustain a magnetic field that was as strong as its gravity, but there was not yet observational evidence to support this prediction. With the two forces balancing out, a cloud of gas caught on top of the magnetic field would be spared the pull of gravity and instead levitate in place.

Read more at: http://phys.org/n...html#jCp

Well, a gas cloud that does not get eaten. Sounds about right. Also, if we apply this type of magnetic field to lesser bodies, we might find that a water veil is created, suspended say, almost 30 miles above the surface of a planet ---like Venus.
Protoplasmix
5 / 5 (1) Jun 05, 2014
With the two forces balancing out, a cloud of gas caught on top of the magnetic field would be spared the pull of gravity and instead levitate in place.

It happens all the time with a solar prominence. The method for evaluating the magnetic stress tensor for an accretion disk (see link in my first post) also describes how a cloud of cool gas in the solar atmosphere (a quiescent prominence) is supported by a magnetic field against gravity. But I don't think 'levitation in place' is the best description.
Osiris1
1 / 5 (1) Jun 05, 2014
Perhaps magnetic fields of sufficient intensity can either control or pull apart 'black holes'. The implications are profound for space travel.
Protoplasmix
5 / 5 (1) Jun 05, 2014
Perhaps magnetic fields of sufficient intensity can either control or pull apart 'black holes'. The implications are profound for space travel.

Depends on the nature of matter. If it's point-like or like 1-d strings or 2-d loops that are crushed/confined in terms of modes of vibration, then probably not. For a laugh, my guess is you could add 3-parts dark energy for every 1-part mass, and turn a black hole white. Quite unrealistic view from inside, would look like a fireball, spacetime expanding, everything redshifted…

O_o
cantdrive85
1 / 5 (3) Jun 06, 2014
Compare this image;
http://en.wikiped...rope.svg
to the image above...

Hi, CD85 – the image in Fig. 2.5 on p. 57 (see link in my previous post) of a jet from a MHD simulation is much closer in appearance to the illustration above. Also, section 2.1 (p. 39-40) gives a derivation of Alven's theorem. What do think about that? Did you read it?

The difference, as usual, is that Alfven's BC description is based upon real plasma experiments developed over decades of research whereas the other is nothing but computer games and theoretical mumbo jumbo of ideal ionized gases (which do not exist in reality).
Captain Stumpy
4.2 / 5 (5) Jun 06, 2014
...whereas the other is nothing but computer games and theoretical mumbo jumbo of ideal ionized gases (which do not exist in reality)
@cd
this is what is called a blatant lie which has been refuted over and over again
MHD also uses alfie's data https://en.wikipe...dynamics
so basically you are calling Alfven a moron by your statements... which is funny
as alfven helped develop MHD models and it was based upon plasma physics and observation, etc and refined to be more accurate
but, astrophysicists also learn about plasma physics and apply it to studies as well as MHD
http://www.pppl.gov/

http://www.physic...-physics

http://phys.color...-physics

it must be nice ignoring empirical data whenever it suits you
cantdrive85
1 / 5 (6) Jun 06, 2014
so basically you are calling Alfven a moron by your statements.

It is really amazing how dense you are, just like a mythical neutron star dense. Alfven proclaimed his mistake prior to being awarded his Nobel and in fact warned scientists against the blanket use with which they apply it to just about every plasma description, as you so helpfully point out. This news is over 40 years old, try and keep up there Einstein...

http://www.nobelp...ture.pdf
Protoplasmix
5 / 5 (2) Jun 06, 2014
The difference, as usual, is that Alfven's BC description is based upon real plasma experiments developed over decades of research whereas the other is nothing but computer games and theoretical mumbo jumbo of ideal ionized gases (which do not exist in reality).

The literature states under which conditions it's acceptable to use equations for the ideal, and when it's necessary to include additional factors/terms as the situation varies.

'BC description' = hypothesis that Birkeland currents give rise to filamentary structures? Huge galactic currents on the order of 10^18 amps? And those have been observed where/when?

Not that there couldn't be such a feature in the universe, but it's been shown that if there was, it would dissipate on time scales far shorter than relevant cosmological scales (see http://arxiv.org/.../0609031 ) and so that's a fairly strong constraint on the hypothesis.
Captain Stumpy
4.3 / 5 (6) Jun 06, 2014
warned scientists against the blanket use with which they apply it to just about every plasma description
@cd
to which we've already shown, time and again, that things have changed in the last 40+ years since alf. made his statement which you obviously KNOW
this news is over 40 years old
so... that would make YOU
mythical neutron star dense
and given that you claim Alf.'s work
is based upon real plasma experiments developed over decades of research
and then turn around and claim MHD
is nothing but computer games and theoretical mumbo jumbo of ideal ionized gases (which do not exist in reality)
then we can conclude that:
1-you don't know physics
2-you are calling Alf. a moron for developing the model
3-you are stuck in the past
4-your admission of the dates above mean that you have not learned ANYTHING NEW since about 1980
5-you can't read (as this has been pointed out many times before)

YOU PROMOTE PSEUDOSCIENCE, NOT SCIENCE

cantdrive85
1 / 5 (4) Jun 07, 2014
Huge galactic currents on the order of 10^18 amps? And those have been observed where/when?


Well, let's see...

http://arxiv.org/...97v3.pdf

Look, right there in the abstract;

"From this data we derive the magnetoplasma and electrodynamic parameters of this 50 kpc long jet. For one component of this jet we obtain for the first time a direct determination of a galactic-scale electric current (∼ 10^18 A) , and its direction − positive away from the AGN. Our analysis strongly supports a model where the jet energy flow is mainly electromagnetic."

So I ask again, is it willful ignorance or intentional misrepresentation (lying)?
cantdrive85
1 / 5 (3) Jun 07, 2014
Sorry Proto, I didn't need to add the accusation of lying, that was highly inappropriate. I'll reserve that for the Stumpy types in these threads.
Protoplasmix
5 / 5 (4) Jun 07, 2014
Thanks for the link, CD85, very cool—someone needs to update the Wikipedia page (plasma cosmology) to reflect that observation and remove the entry stating the contrary.

Furthermore, I applaud the Captain's efforts and have never known him to state anything even remotely misleading, while you have made highly disparaging remarks about the astrophysics community. The link you just provided mentions the efficacy of MHD simulations in a couple places. I don't think it would hurt your cause to apologize to the Cap'n as well astrophysicists and cosmologists in general—in the grand scheme of things, discoveries are being made all the time and in that respect everyone learns new things constantly…
cantdrive85
1 / 5 (3) Jun 07, 2014
Thanks for the link, CD85, someone needs to update the Wikipedia page (plasma cosmology) to reflect that observation and remove the entry stating the contrary.

Good luck with that as there is active censorship occurring on Wiki, science be damned...
http://fascistsou...nection/
Furthermore, I applaud the Captain's efforts and have never known him to state anything even remotely misleading, while you have made highly disparaging remarks about the astrophysics community.

Actually his last statement;
YOU PROMOTE PSEUDOSCIENCE, NOT SCIENCE

is completely fallacious. Plasma Cosmology (Alfven, Peratt) is completely based upon laboratory and in situ scientific research and while Electric Universe (Thornhill,Talbot, Scott) is certainly more speculative in some of it's claims it is based upon the physics derived by the former. His blanket statement deserve contempt. Whereas astros doggedly oppose alternative explanations until in situ measurements are taken, regardless of theoretical explanations.
Captain Stumpy
4.3 / 5 (6) Jun 07, 2014
I don't think it would hurt your cause to apologize to the Cap'n as well astrophysicists and cosmologists in general
@Protoplasmix
That will be interesting... he cannot admit when he is wrong, so I don't see him ever doing this. Thanks for the kudos, though. I appreciate it
Actually his last statement;YOU PROMOTE PSEUDOSCIENCE, NOT SCIENCE
is completely fallacious
@cd
it is the fallacious claims of EU that I argue against, and since you always promote EU, then the comment is true. I don't usually argue against your real science...
In fact, should you start promoting ACTUAL science, then I would not have a problem!

but given your responses to actual physics and your continuing claims which are blatantly false (like ignoring the fact that astrophysicists learn plasma physics, or magnetic reconnection, or"whereas the other is nothing but computer games and theoretical mumbo jumbo of ideal ionized gases (which do not exist in reality)" etc )

EU is pseudoscience
MrPressure
Jun 08, 2014
This comment has been removed by a moderator.
MrPressure
Jun 08, 2014
This comment has been removed by a moderator.
11791
1 / 5 (1) Jun 09, 2014
"Based on the results, the team found not only that the measured magnetic fields can be as strong as a black hole's gravity, but that they are also comparable in strength to those produced inside MRI machines found in hospitals—"

the force exerted inside MRI machines seems a lot weaker than the gravity from black holes.
they dont have their facts correct
Uncle Ira
not rated yet Jun 09, 2014
"Based on the results, the team found not only that the measured magnetic fields can be as strong as a black hole's gravity, but that they are also comparable in strength to those produced inside MRI machines found in hospitals—"

the force exerted inside MRI machines seems a lot weaker than the gravity from black holes.
they dont have their facts correct


Skippy have you ever seen the MRI machine which is big black hole sized? Or a black hole that is MRI machine sized? When sort that question out you can recheck the facts for the correct answer you.