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Spinning Black Hole's Edge Rotates At Nearly the Speed of Light

Soulskill posted about a year and a half ago | from the you-must-be-this-tall-to-ride-the-black-hole dept.

Space 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."

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know your audience (5, Funny)

Anonymous Coward | about a year and a half ago | (#43027803)

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!

Re:know your audience (0)

Anonymous Coward | about a year and a half ago | (#43027861)

Are you..... are you.... serious?

Re:know your audience (1)

cyberchondriac (456626) | about a year and a half ago | (#43027897)

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.

Re:know your audience (3, Insightful)

vux984 (928602) | about a year and a half ago | (#43028297)

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.

Re:know your audience (0)

Anonymous Coward | about a year and a half ago | (#43029097)

If people ask, just tell them it has a lot to do with 'synchrotron radiation'. They'll automatically assume you're talking about something out of a superhero comic book, and if they ever find out you weren't, they'll feel stupid. :D

Re:know your audience (1)

thomasw_lrd (1203850) | about a year and a half ago | (#43028451)

You're obviously not from the deep southern United States.

Mass is at least college level, maybe graduate level.

Re:know your audience (-1, Troll)

gmuslera (3436) | about a year and a half ago | (#43028863)

In that US regions 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.

Re:know your audience (3, Funny)

Anonymous Coward | about a year and a half ago | (#43028939)

No no, a mass is what happens in a Church you heathen.

Re:know your audience (4, Funny)

maxwell demon (590494) | about a year and a half ago | (#43029061)

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!

Re:know your audience (2, Funny)

oodaloop (1229816) | about a year and a half ago | (#43027899)

Of course, it doesn't define accretion, earth, relativistic, radiation, mass, electron, or spin either. If you don't know anything about physics, go post on 4chan or something.

Re:know your audience (1)

Anonymous Coward | about a year and a half ago | (#43027973)

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.

Re:know your audience (1)

MouseR (3264) | about a year and a half ago | (#43028235)

You can thank anonymous postings for this.

Re:know your audience (1)

HairyNevus (992803) | about a year and a half ago | (#43028915)

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.

Re:know your audience (5, Insightful)

nedlohs (1335013) | about a year and a half ago | (#43028259)

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.

Re:know your audience (1)

Anonymous Coward | about a year and a half ago | (#43028759)

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.

Q.E.D., I guess.

Re:know your audience (2)

nedlohs (1335013) | about a year and a half ago | (#43028967)

I didn't want to have to define not, so I just skipped it.

Re:know your audience (1)

alen (225700) | about a year and a half ago | (#43027939)

didn't graduate high school

or did you go to school before the big bang?

Re:know your audience (0)

Anonymous Coward | about a year and a half ago | (#43028263)

didn't graduate high school

or did you go to school before the big bang?

I, in fact, had my big bang after graduating from high school. So, yes, it's pretty much possible that he did.

Re:know your audience (2, Interesting)

Anonymous Coward | about a year and a half ago | (#43028009)

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!

Re:know your audience (0)

Anonymous Coward | about a year and a half ago | (#43028061)

Actually, one of my big complaints about Science Channel styled science shows is the need to take up 3 minutes by giving a definition of a black hole every time they mention a black hole.
 
Take note, podcasters like Pamela Gay: if we haven't gotten the concept of a black hole down by the 10th poscast you've done on the subject then we're just not going to get it.

Re:know your audience (1)

Anonymous Coward | about a year and a half ago | (#43028193)

Actually, one of my big complaints about Science Channel styled science shows is the need to take up 3 minutes by giving a definition of a black hole every time they mention a black hole.

Take note, podcasters like Pamela Gay: if we haven't gotten the concept of a black hole down by the 10th poscast you've done on the subject then we're just not going to get it.

Being a science populizer is a freaking hard thing to do right. And to be honest, the astronomy cast podcasts are independent of one another, so reiterating the definition of a black hole or other "esoteric" astrophysics objects is a good thing for the lay audience.

Re:know your audience (1)

Idbar (1034346) | about a year and a half ago | (#43028081)

It seems like you got caught in the mind-bending relativistic effects of the summary.

Re:know your audience (5, Funny)

140Mandak262Jamuna (970587) | about a year and a half ago | (#43028135)

Till I read the summary I thought ion is a iron with the letter r removed. Now I know what is removed is not r but electrons. Got it.

Re:know your audience (0)

Anonymous Coward | about a year and a half ago | (#43028209)

Exactly.

And even more importantly, why did they leave out possible implications for time travel?

Re:know your audience (4, Insightful)

K. S. Kyosuke (729550) | about a year and a half ago | (#43028223)

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!

Re:know your audience (3, Informative)

voidphoenix (710468) | about a year and a half ago | (#43028833)

It's both, iirc. Star goes supernova, the remnants collapse into a black hole.

Re:know your audience (5, Informative)

smpoole7 (1467717) | about a year and a half ago | (#43028861)

> 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]

Re:know your audience (1)

Artraze (600366) | about a year and a half ago | (#43028303)

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 walruses were in space at all. It's really quite bizarre that the author felt a need to elaborate on that one.

Re:know your audience (1)

PhxBlue (562201) | about a year and a half ago | (#43028837)

Probably so folks wouldn't think it was a typo, e.g., iron iron.

Is the hole rotating, or just the disk? (2, Informative)

ShanghaiBill (739463) | about a year and a half ago | (#43027887)

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? (0)

Anonymous Coward | about a year and a half ago | (#43027951)

Considering they are experienced researchers, how likely do you think is the latter?

Re:Is the hole rotating, or just the disk? (5, Insightful)

Anonymous Coward | about a year and a half ago | (#43028109)

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.

Re:Is the hole rotating, or just the disk? (1)

Anonymous Coward | about a year and a half ago | (#43028183)

The accretion disk and the black hole are not necessarily spinning in sync.

Let's consider angular momentum for a moment. A cloud of gas and dust falls toward a black hole. As it is drawn inward the cloud begins to orbit the black hole forming an accretion disk. As the now ionized gas moves inward, it spins faster and faster. As the matter crosses the event horizon, it is flying around at super speeds. But the event horizon isn't the end. It continues falling inward toward the singularity. Conservation of angular momentum would suggest that it's rotation would continue accelerating as it fell. Faster and faster as it is compressed toward infinite density.

How fast? Well, if the accretion disk near the event horizon is "near the speed of light", I suppose the stuff inside the event horizon would have to be going 'even nearer the speed of light'.

Re:Is the hole rotating, or just the disk? (1)

ceoyoyo (59147) | about a year and a half ago | (#43028795)

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? (0)

Anonymous Coward | about a year and a half ago | (#43029039)

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.

Re:Is the hole rotating, or just the disk? (2)

The Grim Reefer (1162755) | about a year and a half ago | (#43028251)

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.

WRONG! (-1)

Anonymous Coward | about a year and a half ago | (#43027891)

"speed of light" is meaningless -- because it's not a constant. Might as well talk about the "speed of a honda civic". Maybe it's been souped up with a v8 engine and can hit 200mph. Or maybe it's sitting in rush-hour traffic doing 0.

Maybe they mean "speed of light in a vacuum without gravitational interference". But this a is a black hole (the very definition of gravitational interference) so the speed of light may be a constant, but it's not the constant you're thinking of. In fact, it slows down to 0.

Re:WRONG! (1)

jgtg32a (1173373) | about a year and a half ago | (#43027979)

The speed of light is influenced by gravity?

Re:WRONG! (1)

Westwood0720 (2688917) | about a year and a half ago | (#43028011)

Gravity certainly bends light. But as far as slowing it down, I always thought was a constant represented by the letter "c".

light is influenced by gravity (5, Informative)

Anonymous Coward | about a year and a half ago | (#43028049)

http://helios.gsfc.nasa.gov/qa_sp_gr.html [nasa.gov]

" 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:light is influenced by gravity (1)

Westwood0720 (2688917) | about a year and a half ago | (#43028099)

I knew it was something along the lines of that. I recall something about during one of the World Wars a telescope being confiscated for thoughts of being spies, but was given back the day before some astronomers wanted to view the stars behind the sun during a solar eclipse. They did in fact able to see the stars behind the sun showing the world that the sun's gravity bent the light the went around it. This may not be 100% accurate, but I know its something along those lines.

Re:WRONG! (3, Informative)

AK Marc (707885) | about a year and a half ago | (#43028289)

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.

Re:WRONG! (0)

Anonymous Coward | about a year and a half ago | (#43028361)

In some mediums, light moves faster than it does through a vacuum. c is the speed of light in a vacuum, not the "theoretical maximum speed of light"

Re:WRONG! (0)

Anonymous Coward | about a year and a half ago | (#43028393)

Wrong, so very wrong.

Re:WRONG! (2)

MozeeToby (1163751) | about a year and a half ago | (#43028727)

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.

Re:WRONG! (3, Informative)

Anonymous Coward | about a year and a half ago | (#43028159)

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 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.
 
* Yeah, I'm the guy who complained about definitions being used too often in another thread.

Re:WRONG! (0)

thechemic (1329333) | about a year and a half ago | (#43028207)

I think you should have somebody take a look at your shift key.

Re:WRONG! (2)

AK Marc (707885) | about a year and a half ago | (#43028371)

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! (2)

DragonWriter (970822) | about a year and a half ago | (#43028497)

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.

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 holes" as the source or "light" as the affected entity. (As do the more technical, less Science-Channel-ish, works that I've seen addressing the same subject matter.)

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.

The "sucked in" analogy is exactly as accurate (or inaccurate) applied to light as it is to "particles with mass".

Re:WRONG! (1)

maxwell demon (590494) | about a year and a half ago | (#43028499)

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!!!"

Which actually is correct (except for "here" instead of "hear" :-)). What's wrong is the imagination that this is because the light is slowed down when going outwards (actually in some sense the light is slowed down, because the time as seen from outside is slowed down; but that's independent of the direction, and of course locally it is still going with c). The real reason is that the spacetime (not space, spacetime) is curved in a way that there's no way out when going at light speed or below. That is, the outward-going light is still going with light speed, but will not get out, but eventually reach the singularity. Yes, that seems paradox, since the singularity is "in the middle" (which isn't entirely accurate either; for a non-rotating black hole it is actually in the future), but that's because we are not very good in imagining curved four-dimensional spacetimes.

Re:WRONG! (1)

TapeCutter (624760) | about a year and a half ago | (#43028989)

Three dimensions.are mind boggling enough, once you are inside the BH, light is bent such that all directions are pointing towards the "middle", it's sort of like the 3D equivalent of asking which way is north when you are at the south pole.

Re:WRONG! (1)

gmuslera (3436) | about a year and a half ago | (#43028937)

Time and space are influenced by gravity, and speed depends on both.

Re:WRONG! (1)

kenaaker (774785) | about a year and a half ago | (#43027981)

Of course the capitalization of the title is a dead give away. It was nice to self label the contribution.

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! (1)

maxwell demon (590494) | about a year and a half ago | (#43028547)

No, time is the same everywhere, too. Only the length of timelike paths depends on how you move. But ultimately it is not too different from the fact that the length of spacelike paths depends on the way you take. Except that for spacelike paths, the direct path is the shortest, while for timelike paths, the direct path is the longest.

Re:WRONG! (5, Funny)

thechemic (1329333) | about a year and a half ago | (#43028047)

I had a Honda Civic that could go the speed of light. It sucked because nothing ever showed up in the rear view mirror.

Keep going... (1)

mynameiskhan (2689067) | about a year and a half ago | (#43028189)

it is just that our warp tech is not yet caught up with your honda civic.

Re:WRONG! (1)

AK Marc (707885) | about a year and a half ago | (#43028379)

If it's anything like my last Honda Civic, that's because the mirror fell off and is sitting under the passenger seat.

Re:WRONG! (1)

roc97007 (608802) | about a year and a half ago | (#43028505)

...and even with the headlights on, you couldn't see it coming.

Re:WRONG! (1)

oodaloop (1229816) | about a year and a half ago | (#43028777)

And you're always adjusting the in-dash clock.

Re:WRONG! (1)

SJHillman (1966756) | about a year and a half ago | (#43028057)

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.

Re:WRONG! (1)

Turminder Xuss (2726733) | about a year and a half ago | (#43028385)

Doesn't the light have a constant speed for all observers but it's frequency is shifted for an observer in a different frame of reference ?

My thought... (0)

kannibul (534777) | about a year and a half ago | (#43027901)

My thought has always been that black holes are black because the particles they are made from move faster than the speed of light, therefore don't give off light radiation...same with the theory of Dark Matter/Energy....they all contain particles that have aspects that move FTL, and when crossing the FTL barrier means not that it doesn't have mass, that it abnormal mass... But what do I know, I'm not a scientist, or really all that smart. Meh...one of those theories I came up with decades ago after watching too much discovery channel.

Re:My thought... (4, Insightful)

dreamchaser (49529) | about a year and a half ago | (#43028001)

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... (3, Funny)

Talderas (1212466) | about a year and a half ago | (#43028035)

They are obviously made of strawberries and unicorns.

Re:My thought... (0)

Anonymous Coward | about a year and a half ago | (#43028105)

No, the almighty flying spaghetti monster sprinkled Parmesan cheese into the universe to create stars, and shed meatballs to make black holes.

Re:My thought... (1)

PhxBlue (562201) | about a year and a half ago | (#43028867)

They are obviously made of strawberries and unicorns.

I can't prove they're not, so it must be true! </sarcasm>

Re:My thought... (0)

Anonymous Coward | about a year and a half ago | (#43028829)

But what do I know, I'm not a scientist, or really all that smart.

In the future, you should probably focus more on that and less on coming up with novel physical theories.

Re:My thought... (1)

maxwell demon (590494) | about a year and a half ago | (#43029017)

My thought has always been that black holes are black because the particles they are made from

Black holes are not made from particles. Black holes are vacuum. Curved vacuum, that is. Yes, that's hard to understand, because our brain was not made to deal with this. But that's what the mathematics says.

move faster than the speed of light, therefore don't give off light radiation

A charged particle does emit light radiation when going faster than light. This can be observed in a medium (e.g. water) where the speed of light is slower than in vacuum, so particles there can indeed go faster than light (but still not faster than the vacuum speed of light). That radiation is known as Cherenkov radiation. It is the optic analogue of the sonic boom. If the particles could go faster than light in vacuum, they'd emit that radiation also in vacuum.

Uncharged particles would not emit Cherenkov radiation, however uncharged particles don't emit light radiation no matter what their speed is.

Spin equal to mass? (1)

justthinkit (954982) | about a year and a half ago | (#43027917)

Could the near light speed rotation of the SMB be equivalent in some way to having extra mass at the core of the galaxy? In other words, does this change how much dark matter there must be?

Re:Spin equal to mass? (1)

justthinkit (954982) | about a year and a half ago | (#43028063)

Apologies for self-replying...
.

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.

Re:Spin equal to mass? (1)

Antipater (2053064) | about a year and a half ago | (#43028375)

In addition to what the AC said below, it's my understanding that the galaxy rotation problem is a matter of mass distribution, rather than just plain missing mass. Adding more mass to the black hole in the center would make all the stars orbit more quickly, but it wouldn't affect the relative rotational speed from one star to another. In a system where most of the mass is clustered in the center, the outer orbits should have a lower rotational velocity - simply changing the amount of mass at the center won't change that general idea. To explain the uniform speeds going outward from the center, you have to add mass to the edge of the system, rather than the center.

Re:Spin equal to mass? (1)

jkflying (2190798) | about a year and a half ago | (#43028445)

How about a bunch of black holes which are distributed around the edge of the galaxy?

Re:Spin equal to mass? (1)

TheTurtlesMoves (1442727) | about a year and a half ago | (#43029025)

Lots of ideas here. Why don't you run the numbers? Turns out if you do neither of these get close to explaining galatic rotation or other "dark matter" stuff. The facts are that from what we observe, the best explanation/theory right now is dark matter.

Re:Spin equal to mass? (1)

TheTurtlesMoves (1442727) | about a year and a half ago | (#43029049)

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? (4, Informative)

Anonymous Coward | about a year and a half ago | (#43028237)

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.

one question (0)

Anonymous Coward | about a year and a half ago | (#43027983)

But does it run Linux?

Re:one question (2)

gameres (1050972) | about a year and a half ago | (#43028305)

do black holes blend?

Seems obvious to a naive engineer! (4, Insightful)

140Mandak262Jamuna (970587) | about a year and a half ago | (#43028065)

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.

Re:Seems obvious to a naive engineer! (-1, Offtopic)

Anonymous Coward | about a year and a half ago | (#43028315)

ARGGG!!!! Light not escaping a black hole has NOTHING to do with it's gravitational pull. Light has no mass. Multiply any number by zero and you always get zero.

Re:Seems obvious to a naive engineer! (4, Insightful)

Anonymous Coward | about a year and a half ago | (#43028423)

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.

Re:Seems obvious to a naive engineer! (-1)

Anonymous Coward | about a year and a half ago | (#43028471)

Light is affected by the warping of space-time. If you want to talk about relativity maybe you need to learn it yourself.

Re:Seems obvious to a naive engineer! (2, Informative)

Anonymous Coward | about a year and a half ago | (#43028615)

Please feel free to explain the difference between gravity and the warping of space-time by massive objects.

Re:Seems obvious to a naive engineer! (-1, Flamebait)

Anonymous Coward | about a year and a half ago | (#43028827)

Uh, gravitational pull and the warping of time-space, although have the same base cause, are different effects. Sorry if this is a hard concept for you and some of the moderators around here. Go ask an astrophysicist, they'll tell you the same thing.
 
Fuck it, you're probably not smart enough to Google this shit for yourself. I'll just point the way [nasa.gov] .
 
Was that easy enough for you to understand, fucktard?

Re:Seems obvious to a naive engineer! (2)

marcosdumay (620877) | about a year and a half ago | (#43028411)

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.

Re:Seems obvious to a naive engineer! (2)

ceoyoyo (59147) | about a year and a half ago | (#43028875)

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.

I'll belive it when I see it. (0)

Anonymous Coward | about a year and a half ago | (#43028339)

Moving close to the speed of light relative to what?

As with most deep space observatiosn and calculations.... They are all built from a house of cards. Too many assumptions and too many variables. We may soon actually find out that the edge of a blackhole is not moving at all instead of at the speed of light and then a few tweaks to the first theory or a few assumption and bam, yep, now we think its not moving at all.

Re:I'll belive it when I see it. (1)

MozeeToby (1163751) | about a year and a half ago | (#43028769)

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, science will be just as wrong in the future. But there are certain things that just aren't going to change, and the laws of conservation of mass/energy and momentum are one of them.

Information across the event horizon? (2)

Bugler412 (2610815) | about a year and a half ago | (#43028409)

Not a physicist of any kind, but I had thought that information could not cross the event horizon? If that is true, then how can we construe that the speed of matter near the event horizon indicate the speed of rotation of the black hole? Wouldn't it only indicate the speed of that particular matter? Educate me if I'm wrong!

Re:Information across the event horizon? (2)

ceoyoyo (59147) | about a year and a half ago | (#43029101)

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.

But the real question is (-1)

Anonymous Coward | about a year and a half ago | (#43028467)

How do relativistically spinning black holes contribute to global warming, and what can we do about it?

Re:But the real question is (1)

gmuslera (3436) | about a year and a half ago | (#43029029)

Probably the CNN question would be if supermassive black holes are caused by global warming or maybe that they started to rotate so fast due to global warming. Anyway, small things after they ask if the bing bang was caused by global warming.

Rotation speed limiting density? (1)

Bohnanza (523456) | about a year and a half ago | (#43028551)

TFA mentions a fact that I'd read about before, that the black hole's rate of rotation increases as it collapses due to the conservation of momentum. But since no matter can actually mover faster than the speed of light, is the collapse limited by this maximum rotation rate? Would the black hole cease collapsing when the rotation rate neared the speed of light?

Re:Rotation speed limiting density? (1)

MozeeToby (1163751) | about a year and a half ago | (#43028807)

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 particles falling into a black hole.

Re:Rotation speed limiting density? (0)

Anonymous Coward | about a year and a half ago | (#43029053)

No, the speed of light does not limit the angular momentum of a black hole.

Car analogon: Suppose you can accelarate your car infinitely with a constant acceleration. Does that limit the momentum the car can achieve? No, otherwise the conservation of momentum would be violated. The momentum p = m*v can be increased infinitely, but at relativisitc speeds (v is close to c), an increase of momentum does no longer mean an increase of the velocity v (which will always be smaller than c), but an increase of the mass m.

simple explanation for engineers... (0)

Anonymous Coward | about a year and a half ago | (#43028577)

Light (photons) have no mass. Mass will deform the space-time fabric around the object creating a well of sorts. This "space-time well" can be very "deep" for a black hole because is so massive. So deep it can trap light.

The article talks about the implicit spin of a black hole. It is implicit because it can't be measure directly. It is based on the amount of photons (i.e. X-rays) it emits and the difference of those emissions when the black hole is not rotating, is rotating against the debris spiraling into it (accretion disk), or is rotating with the debris spiraling into it. There seems to be correlation between those emissions and the the rate and direction of rotation relative to the accretion disk.

Too simple? (1)

bughunter (10093) | about a year and a half ago | (#43028809)

FTA:

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 supermassive black hole at the center of the spiral galaxy NGC 1365.

If it were a rigid body,

Rotation Rate omega = Tangential Speed nu / 2pi * Radius r = 186 280 mi/s / 6.2832 * 2e6 mi = 0.014824 cyc/sec = 0.88942 cyc/min

Roughly one revolution per minute. Not an amazing rotation rate for objects of scales we're used to, but for something 2 million miles across it's pretty impressive.

Now, an event horizon is anything but a rigid body, so I could be waaaaay oversimplifying. But the article says "imagine a sphere..."

Anyone care to extend the math to apply to something other than the theoretical physicist's favorite imaginary object?

Thought experiment (1)

PhxBlue (562201) | about a year and a half ago | (#43028901)

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?

Re:Thought experiment (3, Informative)

bughunter (10093) | about a year and a half ago | (#43028995)

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.

Re:Thought experiment (2)

bughunter (10093) | about a year and a half ago | (#43029091)

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.

Re:Thought experiment (1)

bryonak (836632) | about a year and a half ago | (#43029105)

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 that the stick must be "soft" enough such that the pressure wave from morsing propagates through with slightly under light speed, so we have an upper bound for the hardest and strongest material in the universe.
I doubt that this would be sufficient to withstand the much larger dimensions involved with this black hole, so even with the "best" material, see the comment above mine.

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