How fast do black holes spin?

Feb 14, 2014 by Fraser Cain, Universe Today
Artist rendering of a supermassive black hole. Credit: NASA / JPL-Caltech.

There is nothing in the Universe more awe inspiring or mysterious than a black hole. Because of their massive gravity and ability to absorb even light, they defy our attempts to understand them. All their secrets hide behind the veil of the event horizon.

What do they look like? We don't know. They absorb all the radiation they emit. How big are they? Do they have a size, or could they be infinitely dense? We just don't know. But there are a few things we can know. Like how massive they are, and how fast they're spinning.

Wait, what? Spinning?

Consider the massive star that came before the black hole. It was formed from a solar nebula, gaining its rotation by averaging out the momentum of all the individual particles in the cloud. As mutual gravity pulled the star together, through the conservation of it rotated more rapidly. When a star becomes a black hole, it still has all that mass, but now compressed down into an infinitesimally smaller space. And to conserve that angular momentum, the black hole's rate of rotation speeds up… a lot.The entire history of everything the black hole ever consumed, averaged down to a single number: the spin rate.

If the black hole could shrink down to an infinitely small size, you would think that the spin rate might increase to infinity too. But black holes have a speed limit.

This video is not supported by your browser at this time.

"There is a speed limit to the spin of a black hole. It's sort of set by the faster a black hole spins, the smaller is its event horizon."

That's Dr. Mark Morris, a professor of astronomy at UCLA. He has devoted much of his time to researching the mysteries of black holes.

"There is this region, called the ergosphere between the event horizon and another boundary, outside. The ergosphere is a very interesting region outside the event horizon in which a variety of interesting effects can occur."

Imagine the event horizon of a black hole as a sphere in space, and then surrounding this black hole is the ergosphere. The faster the black hole spins, the more this ergosphere flattens out.

"The speed limit is set by the , eventually, at a high enough spin, reaches the singularity. You can't have what's called a naked singularity. You can't have a singularity exposed to the rest of the Universe. That would mean that the singularity itself could emit energy or light and somebody outside could actually see it. And that can't happen. That's the physical limitation of how fast it can spin. Physicists use units for angular momentum that are cast in terms of mass, which is a curious thing, and the speed limit can be described as the angular momentum equals the mass of the black hole, and that sets the speed limit."

Scientists measure the spin rates of supermassive black holes by spreading the X-ray light into different colors. Credit: NASA/JPL-Caltech

Just imagine. The black hole spins up to the point that it's just about to reveal itself. But that's impossible. The laws of physics won't let it spin any faster. And here's the amazing part. Astronomers have actually detected supermassive spinning at the limits predicted by these theories.

One black hole, at the heart of galaxy NGC 1365 is turning at 84% the speed of light. It has reached the cosmic speed limit, and can't spin any faster without revealing its singularity.

The Universe is a crazy place.

Explore further: Black hole that doesn't emit x-rays discovered near massive star

add to favorites email to friend print save as pdf

Related Stories

Could we harvest energy from a star?

Feb 04, 2014

Our civilization will need more power in the future. Count on it. The ways we use power today: for lighting, transportation, food distribution and even entertainment would have sounded hilarious and far fetched ...

Supermassive black hole spins super-fast

Feb 27, 2013

Imagine a sphere more than 2 million miles across - eight times the distance from Earth to the Moon - spinning so fast that its surface is traveling at nearly the speed of light. Such an object exists: the ...

Black holes do not exist as we thought they did

Feb 14, 2014

On January 24, the journal Nature published an article entitled "There are no black holes." It doesn't take much to spark controversy in the world of physics... But what does this really mean? In a brief ...

Recommended for you

Kepler proves it can still find planets

Dec 18, 2014

To paraphrase Mark Twain, the report of the Kepler spacecraft's death was greatly exaggerated. Despite a malfunction that ended its primary mission in May 2013, Kepler is still alive and working. The evidence ...

User comments : 27

Adjust slider to filter visible comments by rank

Display comments: newest first

antialias_physorg
5 / 5 (6) Feb 14, 2014
Interesting (to me) question: where does the extra energy go. the black hole seems to want to spin up more and gets prevented to do so. If we're postulating 'endless collapse' (by no means certain) then this would be a classical "insurmountable force meeting an immovable barrier" scenario forthe flattening of the ergosphere against the event horizon.

Those polar points where they (almost) touch must be put through an enormous wringer.
Nestle
1 / 5 (2) Feb 14, 2014
One black hole, at the heart of galaxy NGC 1365 is turning at 84% the speed of light. It has reached the cosmic speed limit, and can't spin any faster without revealing its singularity.
Black holes can reveal their "singularity" through black hole jets. This is just the place, which enables to watch the physical surface ("firewall") of black holes, which is evaporating at this place like the extremely hot star with so-called gravitational brightening at its poles.
Nestle
1 / 5 (2) Feb 14, 2014
The evaporation of matter in fountain from black holes leads to formation of pancake-like shape of galaxies. This evaporation indeed decreases the speed of rotation of black hole gradually, so that the number of jets decreases gradually (in certain stage of this evolution the black holes exhibit the asymmetric jets with character of magnetic monopole). The black holes at the centers of mature galaxies do behave like the dark quiet remnants of the former glory with their event horizon fully closed. The galaxy which has lost its polar jets circulation is slowly returning to its original spherical shape and it changes into elliptic galaxy.

chefykins1
1.5 / 5 (8) Feb 14, 2014
Black holes do not spin because there are NO Black Holes! What they are,are what is known as a Plasma Z Pinch. The Universe is not ruled by Gravity but by Magnetic Force and Electricity. Looks like Einstein's reservations about his Theory of Relativity were correct. Gravity is NOT the ruling force in the Universe.
Peace Y
yyz
5 / 5 (5) Feb 14, 2014
"The evaporation of matter in fountain from black holes leads to formation of pancake-like shape of galaxies....The galaxy which has lost its polar jets circulation is slowly returning to its original spherical shape and it changes into elliptic galaxy."

There are many examples in the literature of SMBHs with jets residing in *elliptical* galaxies. Here are a couple:

http://www.nasa.g...-670.jpg

http://en.wikiped...iSky.jpg

Conversely, we know of SMBHs in "pancake"(disk) galaxies that do not exhibit jet activity (eg NGC 4921 & NGC 1277)

As with your earlier unsubstantiated comments( http://phys.org/n...ive.html ) about the lack of galaxy mergers in the Hubble Deep Field(s) you again display a poor understanding of the current work in the field and astronomy in general.
Urgelt
5 / 5 (3) Feb 14, 2014
Anti put his finger on what's bugging me about this speed limit for spin.

I have to wonder:

- If the spin speed limit is reached, does the singularity stop collapsing? Implying a singularity might not be a point, but have finite dimensions.

- If a singularity continues to collapse to a point, how does excess angular momentum, which cannot be translated into spin, manifest? Energy has to be conserved, doesn't it?

- Does the singularity assume a disk shape due to centrifugal force? If so, how does that affect a black hole's properties?

I don't pretend to understand black holes, but it sure is fun to yak about them. :-)
Captain Stumpy
5 / 5 (5) Feb 14, 2014
What we are witnessing is a Plasma Z Pinch

@chefykins1
links/references?
And as for
the Thunderbolts Project

or
the Electric Universe

it is PSEUDOSCIENCE!
what you are reading/watching is nothing but a bunch of electrical engineers who are trying to make money off of the scientifically illiterate
See:
http://www.tim-th...aqs.html

http://www.tim-th...l_1.html

for starters! there are many more pages out there to see debunking EU

its really simple: electrical engineers dont learn anything about astrophysics
astrophysicists learn a snot-load about plasma, electrical fields, fusion, etc etc etc and put it ALL together into a coherent theory
that is the MAIN REASON that EU cannot bring a viable hypothesis into the astrophysical community
there is some real science, but asking an electrical engineer about astrophysics is like asking a plumber to put out fires/be a firefighter because he knows about how water drains
Nestle
1 / 5 (2) Feb 15, 2014
There are many examples in the literature of SMBHs with jets residing in *elliptical* galaxies. Here are a couple
They could be the result of black hole mergers there. In this case the new pancake-like shape will develop, like at the case of Sombrero galaxy. This doesn't change the fact, the jets and evaporating black holes are typical for young newly formed galaxies with active galactic nuclei.
Nestle
2 / 5 (3) Feb 15, 2014
In 1974, theorists William Press and Saul Teukolsky noted that if a black hole were spinning fast enough, light of a long-enough wavelength passing close by would scatter off it, rather than being sucked in. If this spinning black hole were to be surrounded by something like a mirror, the light could be reflected and scattered many times. Fuelled by energy from the rotation of the black hole, it would bounce back and forth and amplify itself in a runaway process rather like what happens in the mirrored cavity within a laser. If the surrounding mirror were removed or shattered, the light would instantaneously escape in a powerful burst of light and heat – a black hole bomb. Abraham Loeb thinks the primordial black holes might provide an identity for dark matter.
Nestle
2.3 / 5 (3) Feb 15, 2014
I'm sorta confused with this stance, because the primordial black holes were already considered (and never found) as a significant component of dark matter with Randall and Sundrum before twenty years. But these primordial black holes are assumed to be rather small and in AWT they simply correspond the atom nuclei. If Leob thinks about black holes residing at the center of galaxies, then this idea becomes more relevant, because in AWT the galaxies are formed with collapse of dark matter (neutrinos and photons) into quasars and recycle the matter and radiation released with previous generation of galaxies in this way. It would mean, these ideas converge to AWT models, but they're still limited by their adherence on Big Bang cosmology.
chefykins1
1 / 5 (3) Feb 15, 2014
At Captain Stumpy. The Thunderbolts project is staffed by Scientists and what they are saying not only makes sense,but they demonstrate/back up their findings with laboratory experiments and use the work done by other Scientists. As for references : http://www.youtub...;index=1]http://www.youtub...;index=1[/url]
http://www.youtub...;index=1]http://www.youtub...;index=1[/url]
Here's a couple videos of their work Peace Y
Nestle
2.3 / 5 (3) Feb 15, 2014
If you imagine, how such cloud of dark matter collapses into galaxy, then the above idea gives sense in AWT, when the concept of multiverse is taken into account. This moment will represent the nucleosynthesis and atom formation from dark matter - we just need to imagine it like the process widespread around quasars across observable universe. Another article in Nature openly presents the Press & Teucolsky mechanism as an evidence of impossibility of primordial black holes survival (the electron plasma should form an amplifying mirror for the photons bouncing around a black hole).
Nestle
2.3 / 5 (3) Feb 15, 2014
So, now it seems, the physicists did throw the concept of primordial black holes into bin. When they will realize, that these microblackholes are stabilized with extradimensions and they actually represent the common hadrons and atom nuclei formed during nucleosynthesis, they will be forced to reinvent and bring it back.
IMO the level of conceptual confusion in mainstream physics just passed its historical supremum. The physicists already realized, that their simplistic models don't work well, but they still didn't realize, here are alternative interpretations of these models with existing artifacts, which are indeed much more complex, than that - but their similarity is still apparent.
chefykins1
1 / 5 (3) Feb 15, 2014
@ Nestle,I do not doubt that you are,"confused" when it comes to Black Holes and Dark Matter. These are theories that are used by Scientists when their other theories do not match observations as referenced by such noted astronomer/Scientists Halton Arp, Hannes Alfvens,Christian Birkeland et.al. Even Stephen Hawking has to make mathematical adjustments to fit his mathematical theories. Re, there are no black holes,but there are grey ones. Mathematicians have had to constantly add on new mathematical theories when their original theory did not match observations made whereas the Electric Universe theory has pretty much stood pat by their theory(s) as made from laboratory experiments for decades if not Centuries. The Thunderbolts Project is not the only Scientific channel on the Electric Universe. Telluric Current is another channel explaining with more technical answers the workings of the Electric Universe.Hope this helps Peace Y
http://www.youtub...index=10
Nestle
2.3 / 5 (3) Feb 15, 2014
IMO This controversy illustrates the typical attitude of experts, who tend to be more cathegorical in both more dismissial, both acceptance of controversial ideas. Due their specialization they have lowered sense for holistic generalizations, reconcilliation and unification of ideas. After all, the more theories, the more theorists can keep their jobs - so that the experts realy have no problem with their stance from both psychosocial, both socioeconomical reasons.

Niels Bohr: "An expert is a man who has made all the mistakes which can be made in a very narrow field".
Nestle
1 / 5 (1) Feb 15, 2014
Electric Universe theory
is just another level of conceptual confusion here - just from opposite side of cognitive duality (simplistic view vs. overcomplicated one). If you would read the above two articles (1, 2) of Leob, then you would realize, he just uses the electromagnetic plasma explanation for dismissal of primordial black holes. He is cryptoplasmacosmologist so to say. This doesn't change the fact, that this dismissal is speculative and it throws out the baby with the bath water. If the string theorists would be more clever, they would use this controversy for rising of their theory with extradimensions - but they cannot do it, because they did not recognize black holes in common particles anyway. Both sides have their bit of truth, but they cannot admit it openly.
Nestle
3 / 5 (2) Feb 15, 2014
The point of extradimensions is, they not only stabilize the microblack holes against their premature blow with Hawking radiation, but they strongly limit the action of gravitational force (and occasionally the EM forces too) at distance. This eliminates the premature radiation of primordial black holes in presence of electron plasma too. As the result, the resulting hadrons and atom nuclei are pretty stable in this environment - they just don't look like the black holes at all.

The common denominator of all controversies in contemporary physics is, the theorists learned to ignore the classical physics in their deductions - they just consider the quantum gravity theory as something, which deals with vacuum around material particles only at large or small scales. But the subject of quantum gravity is actually everything between dimensional scales of quantum mechanics and general relativity, including these particles itself. The biology and chemistry belong into QG subject too.
chefykins1
2 / 5 (4) Feb 15, 2014
The points I like with Electric Universe/Plasma Cosmology is that they are an inter disciplinary Science that can test their results and Theories in a laboratory . Standard Model Theorists think that Electricity evident is not a significant factor in the Universe because it would upset their entire apple cart,so to speak,and yet it is plain that Electricity/Magnetic Force does indeed play a major part in our Universe. Look at what happened with the Deep Impact Probe. The night before the firing of the probe at the Comet,The Thunderbolts Project predicted what would happen using their Model whereas the N.A.S.A. Scientists were astounded at the results and quite the opposite results occurred from their expected results. I am truly hoping that the Rosetta Probe later this year will finally put to bed the "Dirty Snowball Theory" when it lands on the Comet.I hope it is well shielded from the Plasma tail it will encounter as it comes up from behind.
Peace
Captain Stumpy
5 / 5 (4) Feb 15, 2014
The Thunderbolts project is staffed by Scientists

@chefykins1
electrical engineers (EE), like I said but NOT ASTROPHYSICISTS
what they are saying not only makes sense,but they demonstrate/back up their findings with laboratory experiments and use the work done by other Scientists

no, it DOESNT make sense
it MAY make sense in an EE way BUT
NOT IN ASTROPHYSICS
they are EE's... they do NOT understand astrophysics, because the DO NOT TAKE ALL OF THE ASTROPHYSICAL PARAMETERS INTO CONSIDERATION

like I said ASTROPHYSICISTS LEARN ABOUT PLASMA, ETC
but EE's do NOT learn about astrophysics!
You DO NOT HIRE A FIREFIGHTER TO REPLACE THE PLUMBING ON YOUR HOUSE... you hire a PLUMBER
and STOP USING KNOWN PSEUDOSCIENCE SITES as links
if you want to link, use REAL SCIENCE sites

if your EU is so accurate, there will be peer reviewed studies out there on reputable sites that you can link to
but you wont find anything other than engineering articles/sites and PSEUDOSCIENCE
Captain Stumpy
5 / 5 (4) Feb 15, 2014
The points I like with Electric Universe/Plasma Cosmology is that they are an inter disciplinary Science that can test their results and Theories in a laboratory

@chefykins1
no they are not
they are engineers attempting to talk astrophysics
I guess you were too lazy to read those links I left?
Standard Model Theorists think that Electricity evident is not a significant factor in the Universe

PROVEN FALSE CLAIM
(see: http://phys.org/n...end.html
or: http://phys.org/n...ggs.html )
read the comments and read the links provided
EU has made false claims and you got suckered by them
Electricity/Magnetic Force does indeed play a major part in our Universe

and cosmologists use modern astrophysics that includes this... it is EU that ignores relevant data

you really SHOULD read all those links
EU has made the same claims over and over... which was debunked by authors of studies, as well as other physicists
EU=PSEUDOSCIENCE
alfie_null
not rated yet Feb 16, 2014
I don't pretend to understand black holes

You might be in the minority here (grin).
but it sure is fun to yak about them. :-)

With stipulations, yes indeed. Asking questions like you're doing - yes. Elaborating the science - yes. Preaching to us that all we know is wrong, proselytizing some crank home-grown belief - not a chance.
thermodynamics
1 / 5 (1) Feb 17, 2014
Interesting (to me) question: where does the extra energy go. the black hole seems to want to spin up more and gets prevented to do so. If we're postulating 'endless collapse' (by no means certain) then this would be a classical "insurmountable force meeting an immovable barrier" scenario forthe flattening of the ergosphere against the event horizon.

Those polar points where they (almost) touch must be put through an enormous wringer.


Anti: My understanding is that one means of dissipating energy from the spin of the black hole is through "frame dragging". When any mass spins it is supposed to drag space with it (not something we can really relate to). General relativity predicts frame dragging.

Fleetfoot
5 / 5 (4) Feb 17, 2014
what they are saying not only makes sense,but they demonstrate/back up their findings with laboratory experiments and use the work done by other Scientists

no, it DOESNT make sense
it MAY make sense in an EE way BUT NOT IN ASTROPHYSICS


I object! It doesn't make sense in an engineering way either. From the EE point of view, it is a perpetual motion machine. Stars shine but there is no source of power in their model, magnetic fields create double layers which create currents which form magnetic fields ans on on, round and round, but nowhere is there any source of enegy to keep the whole thing running. The EU model is best summed up as "batteries not included".
Fleetfoot
5 / 5 (3) Feb 17, 2014
"The speed limit is set by the event horizon, eventually, at a high enough spin, reaches the singularity. You can't have what's called a naked singularity. You can't have a singularity exposed to the rest of the Universe. That would mean that the singularity itself could emit energy or light and somebody outside could actually see it. And that can't happen."


What a melodramatic presentation, since the singularity is just a name for the point at the centre, why couldn't they just say "the radius cannot be less than zero". Suggesting that the laws of physics have been concocted to prevent humans seeing something too horrible to contemplate is taking the anthropic principle a bit too far IMHO.
vlaaing peerd
5 / 5 (6) Feb 17, 2014
gives sense in AWT
versus
the workings of the Electric Universe


Good, finally we get the experts talking here. I mean, what do mr Einstein and Mr Hawking really know about black holes, right?

ʇᴉ ʇnɔ ʇ,usǝop ʇsnɾ ɯlɐdǝɔɐɟ pǝsɹǝʌǝɹ ɐ uǝʌǝ ǝɹǝʍ 'suoᴉssnɔsᴉp ƃɹosʎɥd
Osteta
Feb 17, 2014
This comment has been removed by a moderator.
Gawad
5 / 5 (1) Feb 28, 2014
Anti put his finger on what's bugging me about this speed limit for spin.

I have to wonder:

- If a singularity continues to collapse to a point, how does excess angular momentum, which cannot be translated into spin, manifest? Energy has to be conserved, doesn't it?


Yes, momentum, including angular momentum HAS TO BE CONSERVED. And this article does a piss poor job explaining how as the BH reaches its spin limit. Look up the Penrose Process for a clear answer. Briefly, as the rotation increases, the rotating spacetime of the ergosphere becomes increasingly violent, leading to the ejection of some matter away from the BH with more spin than when it approached and the ingestion of correlated matter with less spin. This is what limits the spin, keeping the ring singularity from growing any more and the event horizon from shrinking to meet it.

- Does the singularity assume a disk shape due to centrifugal force?
It becomes ring shaped-2D (at least in the math).
Gawad
5 / 5 (1) Feb 28, 2014
BTW, nothing formally forbids a singularity from being visible and there actually are, theoretically, some (admittedly very unlikely) configurations of matter that would allow this to occur should they collapse. Now, whether this has ever happened or is ever likely to happen in nature is anybody's guess!

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.