Black Hole's Spin Measured by Astronomers

Black Hole's Spin Measured by Astronomers

blackhole

Image Source: NASA
How exactly do you measure the spin of something that is invisible? Astronomers believe they've found a way.

Somewhere, at the center of a spiral galaxy 500 million light years from Earth, a black hole is doing what black holes do best: consuming everything surrounding it. As unwitting planets and stars are sucked into the black hole's maw, matter collects in an accretion disk and begins to orbit the center of the black hole. As more matter is pulled into oblivion, the accretion disk spins faster and faster, like an ice skater executing a tight camel spin.

To measure the spin of a black hole, the research team at Durham University in the UK first measured the distance between the black hole and its accretion disk, using optical ultra-violet and x-rays to view the heat generated as the black hole fed. The logic is simple: the further away the accretion disk is to the black hole, the slower the spin; the closer the disk is to the black hole, the faster the spin. According to the team, the spin on this particular black hole is relatively slow, at least compared to other black holes whose spin has been estimated to be "84 percent of the maximum allowed by Einstein's theory of general relativity," according to Space.com.

Unlocking the spin of a black hole could help astronomers uncover more information about the evolution of galaxies. As black holes chows down at the all-you-can-eat galactic buffet, it spits out incredibly hot particles at high energies. These particles can prevent intergalactic gasses from cooling and forming new stars. Scientists don't know why the particles are ejected into space, but understanding spin could help solve the puzzle. "We know the black hole in the centre of each galaxy is linked to the galaxy as a whole, which is strange because black holes are tiny in relation to the size of a galaxy," says lead researcher Professor Chris Done. "This would be like something the size of a large boulder (10m), influencing something the size of Earth. Understanding this connection between stars in a galaxy and the growth of a black hole, and vice-versa, is the key to understanding how galaxies form throughout cosmic time."

Source: Space.com

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I'm confused, I thought the event horizon of a black hole is determined by its mass, not its spin? Gonna have to read up on it more I guess.

Carnagath:
I'm confused, I thought the event horizon of a black hole is determined by its mass, not its spin? Gonna have to read up on it more I guess.

As far as I understand its the distance between the accretion disk and the event horizon that defines the spin. The spin is important because an active accretion disk generates a perpendicular stream of gas at extremely high energy levels. These gas streams can even raise temperatures in other galaxies and is what gives the black holes their influence. That is my understanding of it anyway.

Anyone else swear the main page banner looks like the outline of the Death Star and its main planetdestructionbeam projector?
OT: Cool. The idea of a black hole is probably the creepiest thing in my mind about space travel. I should never have watched Event Horizon. Damn you Sam Neil for being an excellent creep and damn you Paul W.S. Anderson... for many reasons.

I thought the energy given off by black holes was largely due in part to tearing quantum particles apart from their pairings and sending its twin blasting out into space?

pair quantum particles share the same state so w/e state its twin is trapped in the bh its twin would share it. wonder what would happen if you tried to force a state change in its twin? since you can force them to share states normally, but the physics here say that the twin was ripped into its base "strings?" and mashed onto the surface of the bh written to disk in a sense, trapped in one single state perhaps.

gods now thats going to keep me up at nights now.

cerebus23:
I thought the energy given off by black holes was largely due in part to tearing quantum particles apart from their pairings and sending its twin blasting out into space?

pair quantum particles share the same state so w/e state its twin is trapped in the bh its twin would share it. wonder what would happen if you tried to force a state change in its twin? since you can force them to share states normally, but the physics here say that the twin was ripped into its base "strings?" and mashed onto the surface of the bh written to disk in a sense, trapped in one single state perhaps.

gods now thats going to keep me up at nights now.

Hawking radiation is the main source of energy in an inactive blackhole. Currently its is still unproven by observation but there are unsubstantiated claims. The energy output of Hawking radiation from a supermassive black hole is several million times lower than the energy output from an active one. The polar jets from an active supermassive black hole can be moving at anything up to 99% of the speed of light and can be 100000s of light years long. They are one of the highest energy events in the universe.

albino boo:

cerebus23:
I thought the energy given off by black holes was largely due in part to tearing quantum particles apart from their pairings and sending its twin blasting out into space?

pair quantum particles share the same state so w/e state its twin is trapped in the bh its twin would share it. wonder what would happen if you tried to force a state change in its twin? since you can force them to share states normally, but the physics here say that the twin was ripped into its base "strings?" and mashed onto the surface of the bh written to disk in a sense, trapped in one single state perhaps.

gods now thats going to keep me up at nights now.

Hawking radiation is the main source of energy in an inactive blackhole. Currently its is still unproven by observation but there are unsubstantiated claims. The energy output of Hawking radiation from a supermassive black hole is several million times lower than the energy output from an active one. The polar jets from an active supermassive black hole can be moving at anything up to 99% of the speed of light and can be 100000s of light years long. They are one of the highest energy events in the universe.

Imagine using that as a powersource. Something which will be doable in the faaaaaaaar future if we don't kill ourselves off before we get interstellar travel.

OT: Ineresting stuff, but I admit it flies a little bit above my head. Never get tired of hearing of the weirdness that accompanies black holes though.

Now what I would like to know is what the spin does inside the black hole. Does the spin keep the black hole from shrinking to Planck length? And if so, does that mean matter inside the event horizon can float around and interact? Shame we'll probably never know for sure.

GundamSentinel:
Now what I would like to know is what the spin does inside the black hole. Does the spin keep the black hole from shrinking to Planck length? And if so, does that mean matter inside the event horizon can float around and interact? Shame we'll probably never know for sure.

Whats is been measured here is the spin of mass falling into the the black hole. In the same manner of satellite in a decaying orbit around the Earth, the rotation is independent of the spin, or lack thereof, of the black hole itself.

albino boo:

GundamSentinel:
Now what I would like to know is what the spin does inside the black hole. Does the spin keep the black hole from shrinking to Planck length? And if so, does that mean matter inside the event horizon can float around and interact? Shame we'll probably never know for sure.

Whats is been measured here is the spin of mass falling into the the black hole. In the same manner of satellite in a decaying orbit around the Earth, the rotation is independent of the spin, or lack thereof, of the black hole itself.

That would be the case if the matter didn't interact with the black hole, like a stable satellite orbit. The accretion disc can both add to the spin of the black hole as matter falls in and can be evidence of previous acceleration of the black hole because of past active feeding and the black hole's collapse itself. Plus, it could be slowing it down as the matter gets slowly tidal locked. Not to mention heating/cooling depending on the activity and stability of the black hole.

The more you know i guess. Since some of you seems to know quite a few things about Black Holes. I want to know, since it's spinning faster and faster does it have a chance that one day, it just start sucking what's in our galaxy ?

GundamSentinel:

albino boo:

GundamSentinel:
Now what I would like to know is what the spin does inside the black hole. Does the spin keep the black hole from shrinking to Planck length? And if so, does that mean matter inside the event horizon can float around and interact? Shame we'll probably never know for sure.

Whats is been measured here is the spin of mass falling into the the black hole. In the same manner of satellite in a decaying orbit around the Earth, the rotation is independent of the spin, or lack thereof, of the black hole itself.

That would be the case if the matter didn't interact with the black hole, like a stable satellite orbit. The accretion disc can both add to the spin of the black hole as matter falls in and can be evidence of previous acceleration of the black hole because of past active feeding and the black hole's collapse itself. Plus, it could be slowing it down as the matter gets slowly tidal locked. Not to mention heating/cooling depending on the activity and stability of the black hole.

I said decaying satellite orbit i.e. one that hits the Earth.

For a moment I thought this was about Spoony.

albino boo:

GundamSentinel:

albino boo:

Whats is been measured here is the spin of mass falling into the the black hole. In the same manner of satellite in a decaying orbit around the Earth, the rotation is independent of the spin, or lack thereof, of the black hole itself.

That would be the case if the matter didn't interact with the black hole, like a stable satellite orbit. The accretion disc can both add to the spin of the black hole as matter falls in and can be evidence of previous acceleration of the black hole because of past active feeding and the black hole's collapse itself. Plus, it could be slowing it down as the matter gets slowly tidal locked. Not to mention heating/cooling depending on the activity and stability of the black hole.

I said decaying satellite orbit i.e. one that hits the Earth.

And I said that this decaying orbit would not be independent from the spin of the black hole itself. :D

They did in fact measure the spin of the black hole itself, but they did so by using the spin of the accretion disc and the way it interacts with the warped spacetime around a black hole.

That the disc would spin faster closer to a black hole seems obvious from basic orbital mechanics. But orbital mechanics aren't the only thing that have a say about this, especially since the accretion disc didn't start out spinning (or at least, not as rapidly as it is now). It is spinning so fast because of it's interaction with the sphere of distorted spacetime around the black hole. That distorted spacetime is spinning because the black hole itself is spinning (presumably outrageously fast, if neutron stars are anything to go by) and that in turn is connected with the origin of the black hole. Only accretion matter close to the black hole itself is affected by this and measuring the distance between the black hole and the disc is crucial in finding its spin. And that is what they measured.

At least, that's what I gather from articles about this.

The Floating Nose:
The more you know i guess. Since some of you seems to know quite a few things about Black Holes. I want to know, since it's spinning faster and faster does it have a chance that one day, it just start sucking what's in our galaxy ?

Well, it would only be be able to pull stuff in from further away if it gained more matter, because gravity is proportional to mass. I don't see how increased spin could generate more mass...

I don't really understand what you mean by 'could it suck in stuff that's in our galaxy?' I'm fairly sure there are confirmed black holes in our galaxy, and I'm also pretty sure there's supposed to be a supermassive black hole at the centre of our galaxy. So... yeah? There are totally black holes pulling matter in in our galaxy right now.

The Floating Nose:
The more you know i guess. Since some of you seems to know quite a few things about Black Holes. I want to know, since it's spinning faster and faster does it have a chance that one day, it just start sucking what's in our galaxy ?

It's been theorized that one day black holes will be all that's left of our galaxy. There are several black holes already sucking up matter in our galaxy. There's a very bright radio source near the center of our galaxy called Sagittarius A*, which is very probably a supermassive black hole. Astronomers think there is a supermassive black hole in the center of every galaxy, as the galactic center is a very busy place with lots of chances to suck things up.

Black holes have enormous gravitational force, because they are so heavy, but gravity is also dependent on distance. You have to be very close to be sucked up. If you were to replace our Sun with a black hole of the same mass, the Earth would just continue to orbit it (everything on Earth would be dead because of lack of heat and light, but whatever). And space is so empty around here that that black hole would grow verrrry slowly. But the center of the galaxy is so crowded that stars often intersect eachother and with black holes, so more chance for black holes to feed (even on eachother). But they won't suck up the entire galaxy. It's just too big.

It's theorized that eventually every bit of normal matter will decay (I think I've read somewhere that that will happen in about 10^47 years), and only black holes will remain, slowly deflating through Hawking radiation. It will be a dark time. :(

 

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