Spinning Black Hole's Edge Rotates At Nearly the Speed of Light 227
astroengine writes "Astronomers have directly measured the spin of a black hole for the first time by detecting the mind-bending relativistic effects that warp space-time at the very edge of its event horizon. By monitoring X-ray emissions from iron ions (iron atoms with some electrons missing) trapped in the black hole's accretion disk, the rapidly-rotating inner edge of the disk of hot material has provided direct information about how fast the black hole is spinning. Astronomers used NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) — that was launched into Earth orbit in June 2012 — and the European observatory XMM-Newton measured X-ray radiation as a tool to directly infer the spin of NGC 1365's black hole. 'What excites me is the fact that we are able to do this for the very massive black holes at the centers of galaxies but we can also make the same measurement for black holes in our galaxy ... black holes that resulted from the explosion of a star ... The fact we can extend this from billions of solar masses to 10 solar masses is pretty cool,' Fiona Harrison, professor of physics and astronomy at the California Institute of Technology, Pasadena, Calif., and principal investigator of the NuSTAR mission, told Discovery News."
know your audience (Score:5, Funny)
i love how this summary explains what an ion is, but assumes i know the definitions of black hole, x-ray, and solar mass. great writing, folks!
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Re:know your audience (Score:4, Insightful)
I think everyone sort of knows what a black hole is by now; who hasn't had an x-ray? and mass is just high school chemistry, if not junior high.
Ions are elementary chemistry as well, and are covered early on in school, grade 7 or 8 at the latest I think. Acids and bases, potato batteries, etc.
And knowing what an "x-ray exam" is doesn't tell you anything about what an x-ray actually is, nor what they are doing near black holes.
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You're obviously not from the deep southern United States.
Mass is at least college level, maybe graduate level.
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No no, a mass is what happens in a Church you heathen.
Re:know your audience (Score:4, Funny)
No no, a mass is what happens in a Church you heathen.
Ah, now I understand why the Higgs particle is the god particle: It is causing what happens in a Church!
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Re:know your audience (Score:4, Informative)
In that US region almost everyone would deny all of this, no matter of the education level. The light coming from the accretion disk of that black hole is coming here from before 6000 years ago, when the universe, earth, man, and everything else was created by the almighty god.
I'm an atheist with a college degree who works daily with salt of the earth types in the Bible Belt. In general, physics understanding is spotty around here but actual Young Earthers are extraordinarily rare (to the point where I've never actually met one). You're unlikely to find someone who can tell you the difference between weight and mass and if you want them to use a torque wrench make your specs in foot pounds instead of Newton meters. However, pictures of Jesus riding a T-Rex are taken as ridiculous jokes since, obviously, they weren't contemporaries.
Hell, the guys in the oil and gas industries make their fucking paychecks based on a fundamental understanding of geology, evolution, and the time scales involved.
You may want to question your assumptions more in the future if you would like your worldview to more accurately reflect reality.
Peter
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Ion not an astrophysicist, but ... I did like the way they explained angular momentum. I think everyone sort of knows what a black hole is by now; who hasn't had an x-ray? and mass is just high school chemistry, if not junior high.
Mass is chemistry? damn public school education.
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Re:know your audience (Score:5, Insightful)
That's the point. It wastes a bunch of words explaining what an ion is.
If you don't know what an ion is the rest of the words are going to make any sense anyway.
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I didn't want to have to define not, so I just skipped it.
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You can thank anonymous postings for this.
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As opposed to not knowing what an ion is? If you slept through high school chemistry, Slashdot is happy to dumb everything down for you.
Great evidence of how far this place has fallen.
I don't think anyone who spells out "Slashdot" rather than typing"/." (you know because then the website would be http:///..com [..com]. The whole joke behind why this site is called what it is) is in a position to comment on how far it's fallen. I also don't see how the person who submitted the article explaining the simplest concept in the summary but not the more advanced ones is anything more than curious/funny. Hardly something to read into about the site as a whole.
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didn't graduate high school
or did you go to school before the big bang?
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i love how this summary explains what an ion is, but assumes i know the definitions of black hole, x-ray, and solar mass. great writing, folks!
I love how that part of the summary is plagiarized from the page one of the first article linked and the link takes you to page two!
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Re:know your audience (Score:5, Funny)
Re:know your audience (Score:5, Insightful)
i love how this summary explains what an ion is, but assumes i know the definitions of black hole, x-ray, and solar mass. great writing, folks!
You forgot "space-time", "event horizon" and "accretion disk".
I'm also astounded by the discovery of black holes resulting from an explosion of a star. So far I thought that a black hole is a result of an implosion of a star. This is a major new discovery!
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Re:know your audience (Score:5, Informative)
> I'm also astounded by the discovery of black holes resulting from an explosion of a star.
Really massive stars (greater that 250 solar masses -- i.e., 250 times as massive as our own Sun) most assuredly do explode, and *very* violently, leaving behind a black hole. It's believed that this is a key source for gamma ray burst events. It's also thought that many of the first stars in the universe, not long after the Big Bang, exploded this way, spewing jets of metals at relativistic speeds.
To be fair to you, it's now known that there are actually several different types of supernova. Some core collapses do occur without a big earthshattering "kaboom." The really massive stars explode due to photodisintegration, and result in a hypernova -- a ridiculously intense, you-don't-want-to-be-within-a-hundred-light-years kind of thingie. :)
http://en.wikipedia.org/wiki/Photodisintegration [wikipedia.org]
http://en.wikipedia.org/wiki/Supernova [wikipedia.org]
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And relativistic effects and thus why any of this is even mildly interesting. I guess they explained accretion disc too, though, so that's something.
But beyond that, what I find most awesome about it is that it's completely unnecessary for understanding anything about this. They could've said "X-ray emissions from walruses (large flippered marine mammals) trapped in the black hole's accretion disk" and it wouldn't have really made any difference to 99+% of the audience, aside from causing us to wonder why
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Is the hole rotating, or just the disk? (Score:3, Informative)
Have they shown that the black hole is rotating near c, or just that the accretion disk is rotating near c at the event horizon? The accretion disk and the black hole are not necessarily spinning in sync. If they mean the accretion disk, then, like DUH: if it wasn't rotating near c, it would fall straight in and there wouldn't be a disk.
Re:Is the hole rotating, or just the disk? (Score:5, Insightful)
By monitoring X-ray emissions from iron ions (iron atoms with some electrons missing) trapped in the black hole's accretion disk, the rapidly-rotating inner edge of the disk of hot material has provided direct information about how fast the black hole is spinning.
So the summary indicates that measuring the accretion disk somehow tells them exactly how fast the non-emitting portion is spinning.
The useful answer is in the link from the above quote:
Risaliti and his colleagues measured X-rays from the center of NGC 1365 to determine where the inner edge of the accretion disk was located. This Innermost Stable Circular Orbit - the disk's point of no return - depends on the black hole's spin. Since a spinning black hole distorts space, the disk material can get closer to the black hole before being sucked in.
So they calculated the spin of the black hole by comparing the observed orbit to the calculated orbits possible from the calculated mass based on observable gravitic effect on nearby objects. Yes, there's uncertainty there, but until someone discovers a new detail in astronomy, that's as accurate as we can get.
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Have they shown that the black hole is rotating near c, or just that the accretion disk is rotating near c at the event horizon? The accretion disk and the black hole are not necessarily spinning in sync. If they mean the accretion disk, then, like DUH: if it wasn't rotating near c, it would fall straight in and there wouldn't be a disk.
I realize this is /., but did you not even read the first sentence of the summary?
Astronomers have directly measured the spin of a black hole for the first time
It's not that someone has discovered or theorized about it. They actually measured it. Which I find to be pretty damn interesting.
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That's not actually what happens. The event horizon, among other things, is where general relativity predicts that time will stop. So anything at the event horizon will take forever (literally), from the point of view of an observer at relative rest in flat space, to experience any passage of time. Which means nothing can ever cross the event horizon and continue to fall inward. The event horizon is, very literally, the end.
Re:Is the hole rotating, or just the disk? (Score:4, Informative)
Black holes can evaporate in a few billion years, and then their event horizon disappears. So an event horizon is not the end, just some temporary area with slow time.
A black hole of one solar mass will take 10^67 years to evaporate from Hawking Radiation -- and this time is proportional to the cube of the mass, so think about those SMBHs out there with billions of solar masses. That's a mind-bogglingly long time. You might think it's a long time waiting in line at the Department of Transportation, but that's peanuts compared to black hole evaporation...
And that's only after the CMBR has been red-shifted into near non-existence since until then the black hole is absorbing more energy than it is losing.
Though there are in theory primordial black holes (ones created in the moments after the Big Bang) that would have a lifespan measured merely in billions of years.
Spin equal to mass? (Score:2)
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.
In other words, if a lot of SMB material is moving at close to the speed of light, then this would cause a significant mass increase due to this relativistic effect and so the overall mass of the SMB would be significantly higher...helping to explain the current rotational speed of the stars around the center.
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How about a bunch of black holes which are distributed around the edge of the galaxy?
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What I was describing was a layman's perspective of dark matter. Or are you saying that dark matter doesn't explain galactic rotation or other "dark matter" stuff? Not snark, I honestly can't tell.
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What you said was quite correct.
I'm not sure what they were saying. I think maybe they meant to reply to justthinkit who was actually proposing an alternative?
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then this would cause a significant mass increase due to this relativistic effect.
Sorry no. Relativistic mass increase is not the same as rest mass. So no, when get a particle close enough to the speed of light and it stops accelerating. Its local gravity is determined by its rest mass not its relativistic mass.
Re:Spin equal to mass? (Score:4, Interesting)
Its local gravity is determined by its rest mass not its relativistic mass.
No. Gravity is determined by the stress-energy tensor, and the energy component is total energy, aka relativistic mass (literally, they're the same thing). Relativistic mass is the gravitational mass is also the inertial mass.
A proton's mass -- the ratio between its acceleration and the force exerted by an electric field -- is much higher than the intrinsic mass of the quarks that make it up. It's the kinetic energy of those quarks held together by the Strong Nuclear Force that gives a proton 90% of its mass. The Higgs Field only explains that last 10%.
Similarly the gravity of the sun is far greater than just the intrinsic mass of the quarks and electrons inside it. It's the sum of all energy in the sun.
If you an accelerate an object it gains energy, and therefore (E=mc^2) relativistic mass, and also therefore increased gravity.
Oh, and yes, this means photons have gravity. Not are affected by gravity (though of course they are) but exert it.
Re:Spin equal to mass? (Score:4, Informative)
No. Black holes are not dark matter. Well, I mean, yeah, they are dark. Like black dark. Like "how much more dark could they be? None, none more dark." But they are normal matter, not dark matter. The mass of (nearby) galactic core black holes is easily measured by measuring the speed of closely orbiting stars. Their velocity is entirely dependent on the mass inside their orbit, so no need to invoke dark matter.
Seems obvious to a naive engineer! (Score:5, Insightful)
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Only if that thing is orbiting at the event horizon, what is another way to say that nothing can orbite there. If the object is just falling, it can be slower.
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No, what you said is insightful. IIRC, anything freely falling into a black hole from infinity would arrive at the event horizon travelling at the speed of light. You're also perfectly free to calculate an escape velocity based on relativity. But this measurement is an (indirect) measurement of the rotation (or at least the angular momentum) of the black hole, not the accretion disk.
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Re:Seems obvious to a naive engineer! (Score:5, Interesting)
In my limited understanding of these things, (mostly from articles meant for mass consumption, not scholarly journal papers), I imagine a black hole to be so massive not even light can escape its gravitational pull. Which technically means the escape velocity is the speed of light. So anything at the event horizon should be at the speed of light. This is of course, a naive view. The escape velocity is based on Newtonian, not Relativistic, physics.
In Einstein's theory of general relativity, the Newtonian concept of mass doesn't really exist, being spread out over the Einstein curvature tensor on one side of the general relativity equation and the stress energy tensor on the other. Calculating the radius of a gravitational field where the escape velocity is equal to c is straight forward in both Newtonian mechanics and general relativity, and produce the same value, the so called event horizon (Scharzschild radius, technically) but something interesting happens when the gravitational field is generated by a rotating object -- it drags spacetime around with it. [wikipedia.org] This would cause the orbital plane of an object to precess, something that Newtonian mechanics completely misses but was predicted nearly a century ago when people first started exploring solutions to Einstein's equations. Being able to directly arrive at the rotational rates of a wide variety of blackholes (which is what this announcement is all about) means that both frame-dragging and the no-hair conjecture concerning the characterizability of blackholes with just three Newtonian values -- mass, charge, and angular momentum -- can in principle now be studied more rigorously.
Re:Seems obvious to a naive engineer! (Score:4, Insightful)
Light doesn't have a rest mass, but it most certainly has momentum. Perhaps you need to review what E=MC^2 means, Light is affected by gravity as witnessed numerous times in astonomy. Perhaps your "ARGGG!!!" should be directed at yourself.
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You seem to be unaware of the definition of gravitation.
The effects of the warping of space-time by mass is called gravitation. Your "OMG it's not gravitational pull it's the warping of space-time" line of argument makes no sense considering that gravitation is simply the name we give the warping of space time by mass.
Information across the event horizon? (Score:2)
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You can measure a few properties of black holes. Their mass, charge and angular momentum. All three of these can be observed by the effects they have on nearby matter. The article isn't precisely clear, but I think they're measuring angular momentum by looking at the effect frame dragging has on absorption spectra in the accretion disk.
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Rotation speed limiting density? (Score:2)
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Matter speeds up as the black hole collapses because it moves toward the center of gravity, trading potential energy for kinetic. There's no (practical) limit to the amount of kinetic energy a piece of mass can have, if I have a baseball moving at 99.99999999% the speed of light, I can continue to accelerate that baseball to my heart's content. Though it's acceleration will appear, to an outside observer, to slow down, a baseball's energy will continue to climb at the same rate. The same is true for the
Thought experiment (Score:2)
If I were to build a disc with its inner ring located near (but not inside) the event horizon of this black hole, and an outer ring located a few million kilometers away, at what speed would the outer section of the disc spin? What would happen along that outer edge?
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It would be ripped to shreds by tidal and frame dragging forces, heated to millions of degrees by frictional heating, emit some very lively photons, and the resulting plasma would become part of the accretion disc.
And this is assuming you could even get it in place without the same result befalling the construction crew, their equipment, and raw materials.
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Oh, and also, you'd never live to see the completion of the object because time dilation caused by the mass of the singularity would cause all motion near the event horizon to slow to a virtual stop, as seen by an observer at a reasonably safe distance.
Of course, you can always go visit it yourself to check on the progress... we won't wait for you, though.
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Oh, and also, you'd never live to see the completion of the object because time dilation caused by the mass of the singularity would cause all motion near the event horizon to slow to a virtual stop, as seen by an observer at a reasonably safe distance.
So, kind of like a government contract, then?
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The only thing slower than a contract given to a private company is a task order given to another government agency.
"What, you mean you guys gave me money to do something, and the closest intersection point between our two offices is at the Cabinet level? Yeah, I'll get right on that."
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If I were to take a very long, very rigid (say: diamond) stick with me on one end and someone else sitting on the moon on the other end, then by pushing the stick a bit back and forth we could communicate via the Morse alphabet (ignoring orbital movement, wind drag, etc. for a moment). You'd obviously need something even more rigid (and stronger) than diamond, but keep in mind that light takes some 1.3 seconds for that distance, so this is the maximum speed information can be transmitted with.
This means tha
Reflections (Score:2)
Relativistic Braking? (Score:2)
If the matter on the outer edge of the disc is spinning near the speed of light, and if that matter is gravitationally bound to the rest of the disc and the black hole itself, then eventually the outer edge of the disc should act as a brake on the entire black hole's spin rate (because it can't exceed c). If it were to experience additional imparted momentum, what would happen to spacetime at the edge? I'm curious what the frame-dragging implications of this are.
Is this simply a matter of the amount of ene
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So many people (a number of whom who should know better) get this totally wrong because you always here that a black hole has "such powerful gravity that not even light can escape!!!111!!!"
This is another failing of Science Channel styled science shows*. They neglect to tell you that light doesn't escape because the gravity well created by a black hole warps space, not because photons are pulled on by gravity. It may sound like I'm splitting hairs since the overall end result is the same but a lot o
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It may sound like I'm splitting hairs since the overall end result is the same but a lot of people mistake it as meaning that light is sucked in to the black hole because particles with mass are also sucked in. This also doubtlessly leaves people scratching their head over the misconception that maybe the gravity is forceful enough to actually attact the light.
Light has momentum (which "require" mass in more classical thinking). Light is "moved" by gravity (which indicates mass). If mass distorts space so that it makes light and particles behave the same, then why is it a misconception to think of light as a particle? It's both a particle and a wave, thus *is* a particle.
Re:WRONG! (Score:5, Interesting)
Light has momentum (which "require" mass in more classical thinking). Light is "moved" by gravity (which indicates mass)
Also light has energy which is mass in Relativistic thinking, and is moved by (and moves other things by) gravity which is due to it's energy (same as mass).
This is confusing because people think of "mass" as the things photons don't have and matter does (which is true if we mean intrinsic mass), but also think of "mass" as the thing which effects/is affected by gravity and makes objects resist acceleration, when that's actually the relativistic mass (= energy).
It's both a particle and a wave, thus *is* a particle.
A photon is a quantum mechanical particle, which is a thingie which behaves kinda like a classical particle and kinda like a classical wave but not exactly like either.
However the key thing about quantum mechanics is that stuff is quantized... like particles are. So we call them particles. There is no misconception in doing so.
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If they get too close they no longer can orbit the black hole for the simple reason that they would need to go faster than light to do so.
So you are saying that the singularity curves time-space so much that you'd have to travel infinitely far to be able to leave a black hole, and speed is irrelevant. The light orbits the singularity inside the even
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The only place the light can fully orbit the black hole is exactly at the event horizon, and it is an unstable orbit that would be destroyed by any other near by matter. Once inside the event horizon, light cones all point inward to the point that even at the speed of light, you could not remain at a constant radius from the center.
So light slows down inside singularity? Because at the speed of light, it would be in a stable orbit at the event horizon, right?
And an unstable orbit is an orbit, still a "full" orbit.
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So light slows down inside singularity? Because at the speed of light, it would be in a stable orbit at the event horizon, right?
Yes and no. Light doesn't actually slow down. Time does. If a photon, at 300.000 km/s, gets close to the event horizon time slows down, so while it may still move 300.000 km in a second, that second takes longer and longer to pass. At the event horizon it takes an infinite amount of time.
Therefore if you are looking at it from the outside (and if the light you are using to look with doesn't have these pesky relativistic effects we are talking about) you'd think the photon has stopped.
[/armchair physics
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Most of the Science Channel-style science shows I've seen that cover the issue not only cover that light doesn't escape the gravity well because the gravity of the black hole warps space, but also covered that that's how all gravity works, not just a special variation related to "black h
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For a non-rotating black hole in Schwarzschild coordinates, the radial vector inside the horizon gets timelike, that is, the singularity is not really "in the middle" but "in the future". This quite intuitively explains why you cannot go "outward": The "outward" direction is actually the past direction.
Now, Schwarzschild coordinates are not the full story, but neither are Eddington-Finkelstein coordinates (which obviously are what you had in mind). The complete structure of the Schwarzschild solution can on
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light is influenced by gravity (Score:5, Informative)
" Yes, light is affected by gravity, but not in its speed. General Relativity (our best guess as to how the Universe works) gives two effects of gravity on light. It can bend light (which includes effects such as gravitational lensing), and it can change the energy of light. But it changes the energy by shifting the frequency of the light (gravitational redshift) not by changing light speed. Gravity bends light by warping space so that what the light beam sees as "straight" is not straight to an outside observer. The speed of light is still constant."
Dr. Eric Christian
Re:WRONG! (Score:4, Informative)
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It does not. It only looks that way due to the reactions with electrons.
You must also think that light travels in a straight line?
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You must also think that light travels in a straight line?
Light thinks it does, just like standing on a trampoline and rolling a ball, the ball travels in a straight line, in a curve around you. Gravity curves space such that light travels in a straight line, and the universe curves around it.
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c is a constant represents the theoretical maximum speed of light. The problem is that the speed of light is not constant. Light slows down in a medium.
meh, you are almost right.
C is a constant that represents the maximum speed of light *in a vacuum*.
That "in a vacuum" piece is quite important. The medium itself has no effect on the constant c ( constant is a constant), but each medium has its own value of light propagation speed which is *always* less than c.
Think of 'c' as the speed of reality.
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C is a constant that represents the maximum speed of light *in a vacuum*. That "in a vacuum" piece is quite important.
If there is no material in which light travels faster than C, then your clarification is irrelevant.
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In some mediums, light moves faster than it does through a vacuum.
No, it doesn't. Not only does such a material not exist, it is proven beyond any reasonable doubt to be impossible.
c is the speed of light in a vacuumm
Hey! You got something right!
not the "theoretical maximum speed of light"
And right back to wrong. Nothing can travel through space (empty or otherwise) at faster than c, that is the central concept of relativity.
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In some mediums, light moves faster than it does through a vacuum.
No, it doesn't. Not only does such a material not exist, it is proven beyond any reasonable doubt to be impossible.
That depends on what exactly you mean with the "speed in the medium".
You certainly can have a phase velocity larger than c, and AFAIK you also can have a group velocity larger than c. What you cannot have is a signal velocity larger than c.
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In some mediums, light moves faster than it does through a vacuum.
No, it doesn't. Not only does such a material not exist, it is proven beyond any reasonable doubt to be impossible.
Your statement would seem to be contradicted by this theory [wikipedia.org] on faster-than-c speeds between 2 Casimir plates.
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I take your reasonable doubt and counter it with un-reasonable doubt.
Thats more than enough for many people, sadly.
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The speed of light in a vacuum is a constant. It never changes.
Time, on the other hand, is different almost everywhere. My hypothesis is that the the speed of light and time have switched places in someones private universe.
Re:WRONG! (Score:5, Funny)
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Objects in Mirror are closer than they appear.
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Objects in Mirror are bluer than they appear.
FTFY
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Speed is distance over time. If time slows down, then light will appear to slow down to an observer in another frame of reference. However, speed is unaffected, it takes the same amount of time to cover a set distance within the same frame of reference - it just appears to be slower to an outside observer.
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Re:My thought... (Score:5, Insightful)
You might as well say it's because they are made of rainbows and ponies unless you have math to support your theory.
Re:My thought... (Score:4, Funny)
They are obviously made of strawberries and unicorns.
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They are obviously made of strawberries and unicorns.
I can't prove they're not, so it must be true! </sarcasm>
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If conservation of momentum is preserved (and arguing that it isn't would... well, quite an extraordinary claim) black holes, and the stuff falling into them, are going to be rotating. Unless, I suppose if everything collapsed absolutely, completely, perfectly symmetrically; to an accuracy 1 part in several millions of billions). And even then, as soon as matter starts flowing in the rotational momentum is going to start climbing.
People have it in their heads that since science is wrong in the past, scien
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Definitely a place you'd want to bring a camera to.
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