Cutting through the spin on supermassive black holes

Mar 06, 2013 by Geraint Lewis, The Conversation
How is the spin of black holes measured, and what can it tell us about our universe? Credit: NASA/Goddard Space Flight Center

Astronomers have measured the spin of a black hole buried in the heart of a galaxy located 56 million light years away, and discovered it was spinning quickly – about as quickly as it could go. That was the big news, based on a paper in Nature, in recent days.

So how did the astronomers make their measurement? And what does it mean?

For a long time, black holes were nothing but a theoretical curiosity, but from the 1970s it became clear there were spots in the universe where observational properties could only be due to the presence of an immense .

Within our own galaxy, there are lots of black holes with a mass similar to the sun, but over the last 15 years it has become apparent that hearts of galaxies host supermassive black holes with masses many millions and billions time that of the sun.

Space-time

Supermassive black holes are far too small to be imaged by any telescope we have; and to compound matters, to state the obvious, they are black. But, though physically small, their immense mass ensures their reaches out into the galaxy.

By measuring the speeds of stars orbiting near these central black holes, we can determine the acting on them and measure the mass. This has been spectacularly successful in our own Milky Way, where astronomers have pinned the mass of the central black hole to be more than four million times the .

At such large distances, the gravity the orbiting stars experience carries no information about how quickly the black hole is rotating, and so – to measure this – we need to get a lot closer to the hole, into the regime where gravity no longer resembles the simple laws of Newton. At this point we have to worry about the relativistic effects of Einstein.

In 1963, the New Zealand Roy Kerr cracked the equations for spinning black holes.

At large distances, spinning and non-spinning black holes have the same influence on orbits, tugging on stars in the same way. But as we get closer, the effects of relativity grow, and we find the spinning black hole gives space-time a twist not seen around stationary black holes. And the more a black hole spins, the more space-time is twisted.

Such space-time twists influence the motion of stuff moving close to the black hole, and by tracking nearby orbits we can work out the spin of the black hole. And in this respect we're lucky: falling material rarely drops straight in, but tends to miss and ends up orbiting before making its final plunge.

Accretion disks

Because of the above, some supermassive black holes are surrounded by immense, brightly-glowing accretion disks, with material whizzing around, heating through friction, at speeds approaching that of light.

The arms are in this galaxy are stars. The radiation from the accretion disk is the bright spot at the centre. Credit: John Bahcall/Mike Disney/NASA/ESA

But, even with our best telescopes, all we see is an intense point of light at the heart of a galaxy. So how can we ever see how the accretion disk is moving, and hence work out the spin?

The high temperature of the disk ensures elements such as iron atoms glow brightly, producing sharply-defined emissions of X-ray radiation.

The rapid rotation of the disk means some points are moving towards us, and some away, and the well-known Doppler effect works to change the observed energies of the X-rays, broadening the emission line we observe. So we can measure the speed of the disk rotation.

But as any good car-salesman will tell you, there's more. We have to remember that as this hot material spirals in towards the black hole, the effects of relativity grow larger.

With that in mind, two key features have to be considered.

Mind the gap

The first is the concept of an "innermost stable orbit". In Newtonian gravity, you can safely , without having to use rockets to support yourself, at any height above a massive object.

While this holds for larger orbits around black holes, for material that strays too close, there are no stable orbits and material simply falls in.

If we imagine Earth had an innermost stable orbit at 1000km above the surface, satellites we launched to 1,001km would happily orbit, but those at 999km would simply fall back to Earth.

The existence of an innermost stable orbit means there is a gap in the middle of the accretion disk, a demarcation where matter can happily orbit beyond this distance but rapidly spirals in when the radius is crossed.

Remarkably, the size of the gap depends strongly on the spin of the black hole, with the more twisted space-time of a highly-rotating hole allowing material to orbit closer than that of a stationary black hole.

But material getting closer orbits faster. So if we can see how quickly material is moving (which we determine from the widths of the iron lines) we can start to measure the size of the gap.

The second effect dictates how photons from the accretion disk travel to to telescope. While classical physics tells us that rays travel in straight lines, the warped gravity of Einstein's relativity means that photons can follow complex paths after being emitted, twisting and turning as they climb away from the disk.

Combining these effects means that the nice sharp peaks of iron emission are broadened and distorted, and the shape of the distortion tells us how much the central black hole is spinning.

And this is precisely what is measured.

Why should we care?

We know the supermassive black holes in the heart of galaxies must have been born in the earliest epochs of the universe, probably in the deaths of the first generation of massive stars.

These "seed" black holes must have had masses not much larger than a few hundred or thousand times that of our sun, and so to reach the masses of millions and billions of solar masses, they must have grown rapidly, feeding on in-falling material.

This video is not supported by your browser at this time.
Travel inside a black hole.

It is therefore thought such black holes must have grown with their host galaxies forming around them, and the flow of matter into one is implicitly tied with the flow of matter into the other. And as matter doesn't simply fall directly in, the spins of the host galaxy and central black hole should be similarly related.

So understanding the spins of central gives us clues to how large , such as our own , came into being.

How's that for a positive spin!

Explore further: Radio telescopes settle controversy over distance to Pleiades

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User comments : 35

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cantdrive85
1 / 5 (11) Mar 06, 2013
These two videos show beyond a shadow of a doubt that black holes do not exist in relativity, nor in reality.

http://www.youtub...5InpONK4

http://www.youtub...5O0jTH8A
Q-Star
3.2 / 5 (9) Mar 06, 2013
These two videos show beyond a shadow of a doubt,,,,


,,, that ya probably don't want to get your science lessons from a guy who was kicked out of his graduate program, and later awarded himself a Ph.D.

Stephen Crothers? Aren't ya just a tad embarrassed at using him as a source? Zephyr is a more reliable source than him.
Maggnus
5 / 5 (7) Mar 06, 2013
Stephen Crothers? Aren't ya just a tad embarrassed at using him as a source? Zephyr is a more reliable source than him.


Careful Q, cantdrive can't tell the difference between them. Or them and Leder. Or them and Hoagland.

In fact, you can make up damn near anything, include some graphs, make a nice webpage, and cantdrive will tell everyone how you've shown up every other scientist in the world.
cantdrive85
1.3 / 5 (13) Mar 06, 2013
Rather than attacking the person, which is the M.O. around here, show how he is incorrect. Don't ignore it, he rather simply shows how the math is incorrect, if he is the one who is wrong it should be easy enough for you to point it out. It's the pseudo-skeptic who resorts to ad hominem attacks, this site is rife with them.
Maggnus
4.6 / 5 (10) Mar 06, 2013
Why candrive, so you can ignore them and pretend they were never said in the very next post you make? What's the point of trying to rehash the same thing over and over again with the likes of you, who cannot even take the time to learn the basics of the theories you so abjectly decry?

This site is rife with pseudo-scientific frauds and panderers of snake oil and trinkets. I fart in your general direction.
cantdrive85
1.5 / 5 (8) Mar 06, 2013
Hot gas!
Q-Star
3.7 / 5 (9) Mar 06, 2013
Rather than attacking the person, which is the M.O. around here, show how he is incorrect. Don't ignore it, he rather simply shows how the math is incorrect, if he is the one who is wrong it should be easy enough for you to point it out. It's the pseudo-skeptic who resorts to ad hominem attacks, this site is rife with them.


Here's something to get ya started, plenty of additional links in the article... I bet ya won't even consider reading it.

http://dealingwithcreationisminastronomy.blogspot.com/2009/12/paper-illustrating-more-of-crothers.html

I'm only allowed 1000 characters,,, so if ya need some additional proof of his idiocy, just ask and I'll post more.
Maggnus
5 / 5 (5) Mar 06, 2013
Hot gas!


Lol! So it is! Does that mean it carries a charge?
cantdrive85
1 / 5 (4) Mar 07, 2013
Hot gas!


Lol! So it is! Does that mean it carries a charge?


You'll have to ask an asstrophysicist.
cantdrive85
1 / 5 (6) Mar 07, 2013


Here's something to get ya started, plenty of additional links in the article... I bet ya won't even consider reading it.

http://dealingwithcreationisminastronomy.blogspot.com/2009/12/paper-illustrating-more-of-crothers.html

I'm only allowed 1000 characters,,, so if ya need some additional proof of his idiocy, just ask and I'll post more.

I'm well aware of that crank. A quick read on any one of the rebuttals prepared by those he has misrepresented and misunderstood can show how sadly misinformed this pseudo-skeptic (is he related to you?) really is.
Here is a taste of how truly inept he is...

http://electric-c...utTB.pdf

http://www.sjcrot...man.html

gwrede
4 / 5 (4) Mar 07, 2013
These two videos show beyond a shadow of a doubt that black holes do not exist in relativity, nor in reality.
Hmm. A stand up comedian showing slides of equations he has no clue about. Of course we should believe his hand waving and quips, and agree that Einstein &co don't know crap. Hell, yeah!

cantdrive85
1 / 5 (5) Mar 07, 2013
"Unthinking respect for authority is the greatest enemy of truth." Albert Einstein
barakn
5 / 5 (3) Mar 07, 2013
Where you have written the word "authority," substitute "Anthony Peratt" and then think about it for a while.
Jonseer
1 / 5 (1) Mar 07, 2013
In the video the physicist says "inside the event horizon (of the black hole) space is moving faster than light". (almost at the halfway point of the video. I can't give a time, because vimeo doesn't show that).

That is the first time I have ever heard it said in a scientific context that anything can move faster than light.

Is this a new conclusion, and advance on the old theories that has now been proven sufficiently that it is now accepted by physicists or was he simplifying in a way to make it make sense for the layman but on a deeper level is still false because nothing can move faster than light?
event
5 / 5 (2) Mar 07, 2013
In the video the physicist says "inside the event horizon (of the black hole) space is moving faster than light".

That is the first time I have ever heard it said in a scientific context that anything can move faster than light.

Is this a new conclusion...

No, this has been well known for decades. In fact, during the inflationary phase of the universe, spacetime was expanding many orders of magbitude faster than the speed of light. There is nothing in SR/GR that precludes spacetime from doing so. Only objects with mass are limited to subluminal velocities.
cantdrive85
1.5 / 5 (8) Mar 07, 2013
Where you have written the word "authority," substitute "Anthony Peratt" and then think about it for a while.


The difference between Peratt, Alfven, Birkeland, and such, and Einstein and relativity zealots is experimentation. Einstein and his ilk don't know much about testing their theories/hypotheses in a lab.

"Einstein was quite simply contemptuous of experiment, preferring to put his faith in pure thought." Paul Davies
Tausch
1 / 5 (2) Mar 07, 2013
Crothers stops short of a Hartle–Hawking state - a singularity. He is not going to divide by zero. A universe without mass has no physical meaning for him.

An empty space-time that rotates and an empty space-time that is non-rotating are indistinguishable.
cantdrive85
1 / 5 (4) Mar 08, 2013
A universe without mass has no physical meaning for him.

A Universe without mass has no physical meaning in reality.
Fleetfoot
5 / 5 (2) Mar 09, 2013
When the black hole is formed with singularity and space-time curvature in accordance to general relativity, then it simply cannot spin. Empty space-time cannot rotate (how to measure if its empty) and the singularity can have no momentum.


In the spinning case, the singularity becomes a ring which then produces frame dragging effects as it spins.
ValeriaT
1 / 5 (3) Mar 09, 2013
In the spinning case, the singularity becomes a ring which then produces frame dragging effects as it spins.
This is said about event horizon which is of finite surface area - but how the infinitely thin singularity ring can exhibit dragging effects? These schematic ideas completely neglect the quantum mechanics - not to say about dense aether model.
Fleetfoot
5 / 5 (4) Mar 09, 2013
In the spinning case, the singularity becomes a ring which then produces frame dragging effects as it spins.
This is said about event horizon which is of finite surface area - but how the infinitely thin singularity ring can exhibit dragging effects?


In GR, all effects come from the stress-energy tensor whose components include flow of momentum. The ring contains the mass which has fallen in and is rotating, it has angular momentum so it causes frame dragging effects.

These schematic ideas completely neglect the quantum mechanics


Right, the nature of the composition of the ring itself requires QM so we cannot say anything about that detail but GR models the macroscopic effects so is still applicable.

not to say about dense aether model.


Good, until you learn why gas cannot support transverse waves, saying nothing is the best approach.
ValeriaT
1 / 5 (3) Mar 09, 2013
until you learn why gas cannot support transverse waves, saying nothing is the best approach
The AWT is based on dense gas model, which behaves like the supercritical fluid in certain extent. The supercritical fluid is elastic gas, which spreads substantial portion of energy in transverse waves along its density fluctuations. These fluctuations have character of sparse dynamic foam, which may serve as a low density analogy of vacuum.

One of reasons, why the dense aether model survived in safety one hundred years of mainstream physics development is, the contemporary physicists aren't even able to imagine, how the dense gases actually work and how they spread the energy. It's sorta mental block - not just conscious antipathy.
Fleetfoot
5 / 5 (4) Mar 10, 2013
until you learn why gas cannot support transverse waves, saying nothing is the best approach
The AWT is based on dense gas model, which behaves like the supercritical fluid in certain extent. The supercritical fluid is elastic gas, which spreads substantial portion of energy in transverse waves along its ...


"Along" is longitudinal. "Transverse" means "across", at right angles to "along".

density fluctuations.


Transverse waves do not involve changes of density, they are a sideways motion of the bulk material that leave density unaffected.

One of reasons, why the dense aether model survived in safety one hundred years of mainstream physics development ....


There is and never was any such theory, Lodge's talk was nothing more than speculation, he never turned into a theory.

This is primarily cluelessness on your part, you are describing longitudinal waves, you don't appear to know what the word "transverse" means.
ValeriaT
1 / 5 (3) Mar 10, 2013
"Along" is longitudinal. "Transverse" means "across", at right angles to "along".
OK, why not.. Does the transverse water wave spread ACROSS or ALONG water surface?
Transverse waves do not involve changes of density, they are a sideways motion of the bulk material that leave density unaffected.
Yes, this is a good insight. But being utterly consequential - is such a situation physically possible? Or is is just an useful extrapolation? In AWT every transverse wave makes the surface deformed and as such slightly more dense temporarily, or it would violate the mass-energy equivalence.
Lodge's talk was nothing more than speculation, he never turned into a theory.
OK, lets talk about hypothesis.
you are describing longitudinal waves, you don't appear to know what the word "transverse" means
This is adhominem fallacy. Just explain, why do you think so - or don't spread claims about my qualifications. After all, even if I wouldn't understand it, what would change it?
Fleetfoot
5 / 5 (3) Mar 10, 2013
"Along" is longitudinal. "Transverse" means "across", at right angles to "along".
OK, why not.. Does the transverse water wave spread ACROSS or ALONG water surface?


We are talking about waves in the bulk of the material, not on the surface, and fluid cannot transmit them, only solids.

A horizontal transverse seismic wave in rock would be a north-south displacement if the wave was moving from west to east.

Transverse waves do not involve changes of density, they are a sideways motion of the bulk material that leave density unaffected.
Yes, this is a good insight. But being utterly consequential ..


No, it is key. Longitudinal waves propagate because the compression which causes the higher density also increases pressure which provides the restoring force. In transverse waves that doesn't happen, it is the shear stress in the rock that restores the displacement. Fluid and gas have no shear strength hence transverse waves cannot propagate through them.
Fleetfoot
5 / 5 (3) Mar 10, 2013
"Along" is longitudinal. "Transverse" means "across", at right angles to "along".
OK, why not.. Does the transverse water wave spread ACROSS or ALONG water surface?


We are talking about waves in the bulk of the material, not on the surface, and fluid cannot transmit them, only solids.

A horizontal transverse seismic wave in rock would be a north-south displacement if the wave was moving from west to east.


Transverse wave from an earthquake near the surface moving down towards the centre of the Earth have displacements that are horizontal, any mix of north-south and east west. The critical point is that the restoring force is the strength of the rock, not gravity or any other external directional force.
Fleetfoot
5 / 5 (3) Mar 10, 2013
you are describing longitudinal waves, you don't appear to know what the word "transverse" means
This is adhominem fallacy.


No, it is not ad hominem, I am commenting on what you wrote, not you as a person.

Just explain, why do you think so


Because you wrote: "gas, which spreads substantial portion of energy in transverse waves along its density fluctuation". Sound is the form of wave that propagates as density and pressure changes so you gave a reasonable description of it, but it is a good description of a longitudinal wave, not transverse.

or don't spread claims about my qualifications.


I have never mentioned your qualifications.
ValeriaT
1 / 5 (3) Mar 10, 2013
No, it is not ad hominem, I am commenting on what you wrote, not you as a person.
So you even don't know, what the ad hominem falacy is. What I know or not is solely irrelevant to subject, as my replies could be correct quite accidentally. BTW I am only commenting on what you just wrote, not you as a person....
gas, which spreads substantial portion of energy in transverse waves along its density fluctuation
The trick of waves inside of particle environment is, they're never purely transverse or solely longitudinal ones, but always the mixture of both. In addition, with increasing density of gas there is a seamless transition between both types of waves and the density perceived depends on reference frame in addition. So for example, from outside the black hole may appear like the dispersive environment full of longitudinal waves, whereas from inside it appears like smooth homogeneous environment.
Fleetfoot
5 / 5 (2) Mar 10, 2013
No, it is not ad hominem, I am commenting on what you wrote, not you as a person.
So you even don't know, what the ad hominem falacy is.


http://www.skepdi...nem.html

You are confusing the evidence presented with a conclusion that might be drawn from it. I quoted your own words where you gave a description of a longitudinal wave and claimed you were describing a transverse wave. I did not imply that should be taken to reflect on you as a person, the "ad hominem" part. It seems you are the one who does not know what the term means.

What I know or not is solely irrelevant to subject,


It is very relevant because longitudinal waves do propagate in a gas while transverse waves do not, so exchanging the names is a critical error.

BTW I am only commenting on what you just wrote, not you as a person....


As was I, hence there is no ad hominem content on either side.
Fleetfoot
5 / 5 (3) Mar 10, 2013
The trick of waves inside of particle environment is, they're never purely transverse or solely longitudinal ones, but always the mixture of both. In addition, with increasing density of gas there is a

http://www.aether...sity.gif


That isn't a gas, this is:

http://upload.wik...tion.gif

From:

http://en.wikiped...c_theory

What you've drawn is a solid with pressures between the component parts where they are in contact fixing their spatial relationships. What distinguishes a gas is that it has no fixed shape or volume, your diagram shows both as fixed.
ValeriaT
1 / 5 (3) Mar 10, 2013
What distinguishes a gas is that it has no fixed shape or volume, your diagram shows both as fixed.

The animated diagram doesn't illustrate particles of gas, but a density fluctuations of it. The density fluctuations inside of dense gas have foamy character, which enable the propagation of transverse waves along it.
Fleetfoot
5 / 5 (3) Mar 10, 2013
What distinguishes a gas is that it has no fixed shape or volume, your diagram shows both as fixed.

The animated diagram doesn't illustrate particles of gas, but a density fluctuations of it.


Nope, as the caption states, it illustrates individual particles. The number of particles in the box is constant hence so is the density.

The density fluctuations inside of dense gas have http://www1.chem....o24.jpg, which enable the propagation of transverse waves along it.


You are still describing longitudinal waves, not transverse. Try to learn the difference.
ValeriaT
1 / 5 (2) Mar 10, 2013
Nope, as the caption states, it illustrates individual particles. The number of particles in the box is constant hence so is the density.
In dense aether theory everything is formed with density fluctuations, individual particles don't exist in this model.
You are still describing longitudinal waves, not transverse.
Nope, at the moment, when the foamy density fluctuations inside of dense gas become dominant, the most of energy is spreading along surfaces of its membranes in transverse waves - not in longitudinal waves through the bulk.
ValeriaT
1 / 5 (2) Mar 10, 2013
BTW Whereas I do believe you, you've experience with mainstream physics, you're demonstrating rather clearly, that the intuitive understanding of reality is something, which is very distant to your way of thinking.
Fleetfoot
5 / 5 (3) Mar 11, 2013
Nope, as the caption states, it illustrates individual particles. The number of particles in the box is constant hence so is the density.
In dense aether theory everything is formed with density fluctuations, individual particles don't exist in this model.


Then it isn't a gas, what you drew was a solid.

You are still describing longitudinal waves, not transverse.
Nope, at the moment, when the foamy density fluctuations inside of dense gas become dominant, the most of energy is spreading along surfaces of its membranes in transverse waves - not in longitudinal waves through the bulk.

What you drew looks like fine grained metal just like the old 19th century crystalline aether and bears no resemblance to Lodge's ideas.

You're demonstrating rather clearly, that the intuitive understanding of reality is something, which is very distant to your way of thinking.


No, I'm demonstrating that you don't know what words like "solid" and "gas" mean.