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The Fate of the First Known Black Hole

Soulskill posted more than 2 years ago | from the black-holes-and-revelations dept.

Space 67

sciencehabit writes "Cygnus X-1 bears its name because it was the first source of x-rays found in the constellation Cygnus. In 1971, astronomers discovered that the x-rays came from the direction of a bright blue star whirling around a mysterious dark object. They speculated that the x-rays were resulting from material being torn away from the bright star and falling onto the dark object, perhaps a black hole. This year, astronomers established that Cygnus X-1 does indeed harbor a black hole, a dead star whose great gravity lets nothing, not even light, escape. Now that result has inspired a forecast for the system's future: The black hole will swallow even more mass from an unfortunate star circling it, then likely dash away on its own when its companion explodes."

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67 comments

There's an important lesson for physicists in this (2, Funny)

idontgno (624372) | more than 2 years ago | (#37027926)

Never, ever, EVER bet against Rush. [wikipedia.org] Ever.

Steven Hawking, [techie-buzz.com] I'm looking at you.

Re:There's an important lesson for physicists in t (2, Funny)

Anonymous Coward | more than 2 years ago | (#37028096)

I think Steven Hawking's Speak and Spell should be auto tuned to Geddy Lee's High Falshetto.....

Re:There's an important lesson for physicists in t (1)

Canazza (1428553) | more than 2 years ago | (#37030444)

someone needs to redub Hawking's lines in this then
http://www.youtube.com/watch?v=zSgiXGELjbc [youtube.com]

Re:There's an important lesson for physicists in t (0)

Anonymous Coward | more than 2 years ago | (#37033850)

Completly off topic but I think it would be funny to hack Hawking's speech box so that in the middle of a speech it would say something like 'I like turtles' and then a complete rant about why :)

Might be cruel but funny IMO

Re:There's an important lesson for physicists in t (2)

Daetrin (576516) | more than 2 years ago | (#37028926)

Invisible to telescopic eye
Infinity, the star that would not die

All who dare to cross her course
Are swallowed by a fearsome force

Re:There's an important lesson for physicists in t (1)

Anonymous Coward | more than 2 years ago | (#37029334)

for she has the face of a horse
and the ass of an otter
she eats and eats and eats and eats
she's your fat mother.

Re:There's an important lesson for physicists in t (0)

Anonymous Coward | more than 2 years ago | (#37030004)

Man, that black hole is so big, it's even capturing the limelight.

Re:There's an important lesson for physicists in t (2)

Canazza (1428553) | more than 2 years ago | (#37030436)

So... if they were right about that... what does that mean for us in 101 years time?

Little Known Fact (1)

Anonymous Coward | more than 2 years ago | (#37027972)

The mound is the hole's only natural enemy.

if black holes attract light (2)

decora (1710862) | more than 2 years ago | (#37027988)

then does light also attract black holes?

that is, does light exert a gravitational force on other celestial entities?

then, the next question, how fast is that force of gravity propagated?

Re:if black holes attract light (0)

Anonymous Coward | more than 2 years ago | (#37028038)

Yes, and at the speed of light in actuality but as if it were instantaneous in practice, due to relativistic effects. Check out reddit.com/r/askscience and search. These questions have been answered there many times.

Re:if black holes attract light (2)

Ambitwistor (1041236) | more than 2 years ago | (#37028080)

Light gravitates, albeit very weakly. Everything gravitates.

Changes in the gravitational field propagate at the speed of light, according to relativity theory. This has never been measured directly (although the LIGO observatory is being upgraded to hopefully do so). But the 1993 Nobel Prize in physics was awarded for astronomical work that demonstrated this indirectly.

Re:if black holes attract light (0)

Anonymous Coward | more than 2 years ago | (#37028204)

Any item with mass possesses gravity. Light consists of photons, which are massless, and therefore do not exert gravity.

Technically, gravity is the curvature of space-time. As any item moves through space-time, it follows the natural curvature, which affects its trajectory. Thus planets could be said to move in a straight line through curved space as they orbit stars. Light, too, must move through space time, and if it enters the event horizon of the singularity, it cannot escape.

Re:if black holes attract light (2)

GrumpySteen (1250194) | more than 2 years ago | (#37028304)

"Since photons contribute to the stress-energy tensor, they exert a gravitational attraction on other objects, according to the theory of general relativity."

Source [wikipedia.org]

Feel free to scroll down to reference #85 for the references listings if you should want to make sure that Wikipedia has summarized them correctly.

Re:if black holes attract light (2)

Ambitwistor (1041236) | more than 2 years ago | (#37028318)

As another poster pointed out, photons possess energy and therefore gravitate. This is a corollary of relativistic mass-energy equivalence (E=mc^2).

Re:if black holes attract light (5, Informative)

Chris Burke (6130) | more than 2 years ago | (#37028436)

This is a corollary of relativistic mass-energy equivalence (E=mc^2).

A lot of people (and I sympathize because I was one of them for years) mistakenly believe that E=mc^2 is about the energy content of matter, and how you could convert mass to energy via, say, matter/anti-matter annihilation. Which when thought of as converting one form of energy to another is true, but hides the deeper truth: Matter isn't just a type of energy that has mass, all energy has mass, they are really the same thing.

Re:if black holes attract light (0)

Anonymous Coward | more than 2 years ago | (#37030474)

So, you're say that...all matter is merely energy... condensed to a slow vibration... we are all one consciousness experiencing itself subjectively and there's no such thing as death, life is only a dream, and we're the imagination of ourselves?

Woah.

Re:if black holes attract light (2)

Talderas (1212466) | more than 2 years ago | (#37031480)

Who let Keanu Reeves on Slashdot?

Come on. Speak up. I promise I will give you 10 seconds to run before the lynch mob starts.

Re:if black holes attract light (0)

Anonymous Coward | more than 2 years ago | (#37034074)

You need a search going.

Re:if black holes attract light (1)

Thiez (1281866) | more than 2 years ago | (#37031546)

How exactly does
> we are all one consciousness experiencing itself subjectively and there's no such thing as death, life is only a dream, and we're the imagination of ourselves
follow from
> all matter is merely energy
?

Do explain.

Re:if black holes attract light (2)

SleazyRidr (1563649) | more than 2 years ago | (#37032470)

It's a Bill Hicks bit. I don't know what show it was part of, but I can tell you that it was sampled on the hidden track on one of Tool's albums.

Re:if black holes attract light (2)

Chris Burke (6130) | more than 2 years ago | (#37028348)

Any item with mass possesses gravity. Light consists of photons, which are massless, and therefore do not exert gravity.

Any item with mass possesses gravity, and light consists of photons, which have energy and therefore mass [wikipedia.org] . The mass of a system is directly proportional to its energy content, as energy is lost so too must mass. An object emitting photons is losing energy and therefore mass, an object absorbing photons is gaining energy and therefore mass.

Photons have no rest mass as far as we know, but that's not the same thing. The total mass of a system containing photons is greater, due to the photon's energy, than a system without. Photons on their own are energy, and therefore exhibit mass, however tiny, and therefore themselves bend space time.

Re:if black holes attract light (0)

Anonymous Coward | more than 2 years ago | (#37035828)

Photons have no rest mass as far as we know, but that's not the same thing.

Actually, where photons are concerned, yes, it is.

Einstein's full equation is
E^2 - (pc)^2 = (m c^2)^2
E is energy, p is momentum, c is the speed of light and m is the rest mass (if you want the derivation, this is the 2-norm of the momentum four-vector). Rest mass, though, is a relativistic invariant — all observers, in all inertial coordinate frames, agree on its value. For photons, all observers agree: the photon has no mass, whence follows the usual result for photons
E = pc

So, if an object gains or loses mass on absorbing a photon, it's not because the photon has mass, it's because the photon has energy.

-JS

Yes, I am a physicist.

Re:if black holes attract light (1)

Chris Burke (6130) | more than 2 years ago | (#37036248)

So, if an object gains or loses mass on absorbing a photon, it's not because the photon has mass, it's because the photon has energy.

And the object does gain (relativistic) mass because it gained energy and energy is mass, so the object having more energy means it has more mass. The photon having energy means it has relativistic mass.

Yes, I am a physicist.

Which explains why you're using "mass" to mean "rest mass", because that's the only time you're talking about "mass" that isn't synonymous and thus redundant with "energy".

But for people who haven't internalized mass-energy equivalence, that Conservation of Mass is just a re-statement of Conservation of Energy, it's important to separate 'mass' and 'rest mass'. After all, 'rest mass' is not conserved.

Re:if black holes attract light (1)

snowgirl (978879) | more than 2 years ago | (#37028676)

Any item with mass possesses gravity. Light consists of photons, which are massless, and therefore do not exert gravity.

Technically, gravity is the curvature of space-time. As any item moves through space-time, it follows the natural curvature, which affects its trajectory. Thus planets could be said to move in a straight line through curved space as they orbit stars. Light, too, must move through space time, and if it enters the event horizon of the singularity, it cannot escape.

Photons have a zero REST MASS. But by having velocity, they have relativistic mass.

Re:if black holes attract light (1)

tendrousbeastie (961038) | more than 2 years ago | (#37035448)

Isn't relativistic mass just a function of rest mass, probably using some Lorentzian style root 1 minus c squared over v squared type thing?

Is rest mass is zero then relativistic mass would be zero too?

(If photons had mass due to special relativistic effects then that mass must be infinite, as photons move at c, and special relativistic equations are all based on the ratio of velocity to c)

Surely photonic space-time curvature comes from their energy, not their mass? (e = hf from Max Plank, so photons have a hugely tiny amount of energy each, and ST distorts in response to matter and energy)

Re:if black holes attract light (1)

Chris Burke (6130) | more than 2 years ago | (#37036662)

Isn't relativistic mass just a function of rest mass, probably using some Lorentzian style root 1 minus c squared over v squared type thing?

Is rest mass is zero then relativistic mass would be zero too?

(If photons had mass due to special relativistic effects then that mass must be infinite, as photons move at c, and special relativistic equations are all based on the ratio of velocity to c)

Relativistic mass is E/c^2. The reason an object with rest mass moving at c would have infinite mass is because it would have infinite kinetic energy.

Surely photonic space-time curvature comes from their energy, not their mass?

Well if you mean rest mass then obviously not because photons don't have any, and if you mean relativistic mass then you just said is equivalent to "space time curvature comes from their energy, not their energy". It's a tricky thing, because once you accept mass-energy equivalence, then there's little point to talking about any kind of 'mass' except rest mass aka invariant mass.

So the best way to say it would probably be that yes, photons curve space time because of their energy, just like everything else. :)

Re:if black holes attract light (1)

Ambitwistor (1041236) | more than 2 years ago | (#37037252)

Depends on how you define "relativistic mass". You can define it as E/c^2, and relate it to "rest mass" by a Lorentzian gamma factor. But this doesn't work if you try to plug relativistic mass into Newton's law; it turns out that you need a whole "relativistic mass matrix" instead of a scalar. This matrix can be decomposed into "longitudinal" and "transverse" relativistic mass. See Wikipedia [wikipedia.org] for more.

"Invariant mass" or just "mass" is a better term than "rest mass", since it applies to photons. (Photons are never at rest and therefore it is meaningless to ask what their mass "at rest" would be.) For a photon, (invariant/"rest") mass is zero, but its relativistic mass (via the E/c^2 definition) is not.

The gravitational effect of a photon depends on its relativistic mass-energy (E, or E/c^2, depending on how you look at it), not its invariant mass (=0).

Re:if black holes attract light (1)

boristhespider (1678416) | more than 2 years ago | (#37031264)

Damn it! That's my entire career invalidated! If only someone had told me that I shouldn't include photons in the Einstein equations!

You know, it's even worse than that. No-one told me that I shouldn't include their pressure, either! Oh man, I've seriously been getting it wrong. Thank you, Anonymous Coward. I'll never make that mistake again!

Re:if black holes attract light (0)

Anonymous Coward | more than 2 years ago | (#37028098)

then does light also attract black holes?

that is, does light exert a gravitational force on other celestial entities?

then, the next question, how fast is that force of gravity propagated?

IANAA (I am not an astrophysicist) but AFAIK:

Gravity attracts everything including light. More gravity, more attraction, light gets bent more. This can be observed through gravitational lensing when looking at a far away but very large object (like another star) you can actually see stuff behind it because the light from THAT object has bent around the star a little.

Black holes have the most gravity and therefore exert the strongest pull on light, so strong in fact that light cannot escape the pull of one within a certain distance (and gravitational strength)

Light doesn't attract anything except my cat.

---

Your last questions is interesting but I've never heard of gravity having a speed, it simply 'exists' and exerts an effect on nearby space. The idea of an 'infinitely fast' gravity is a very curious thought.

Re:if black holes attract light (-1)

Genda (560240) | more than 2 years ago | (#37028144)

No, light does not attract black holes, how ever the barionic objects that produce the light do.

Light exerts force on all objects with mass, in fact one of the more interesting interplanetary/interstellar ship designs involves shooting a laser at a large light sail.

We are still trying the prove there are gravity waves, we have yet to actually measure them so we have no idea yet how fast they propagate, though some think the graviton is likely to be a tachyon (a particle that is faster than light.) Measuring gravitons is operationally impossible: [wikipedia.org]
Unambiguous detection of individual gravitons, though not prohibited by any fundamental law, is impossible with any physically reasonable detector.[11] The reason is the extremely low cross section for the interaction of gravitons with matter. For example, a detector with the mass of Jupiter and 100% efficiency, placed in close orbit around a neutron star, would only be expected to observe one graviton every 10 years, even under the most favorable conditions. It would be impossible to discriminate these events from the background of neutrinos, since the dimensions of the required neutrino shield would ensure collapse into a black hole.

Re:if black holes attract light (0)

Anonymous Coward | more than 2 years ago | (#37028430)

WOW, I can't even begin to handle how much is wrong with that statement.

Just wow.

Actually, the referenced paper says something else (2)

tlambert (566799) | more than 2 years ago | (#37028916)

Actually, the referenced paper says something else.

They specifically talk about the LIGO II http://www.ligo.org/ [ligo.org] gravity wave observatory. And yes, they believe that a gravity wave can be detected without having the ability to detect individual gravitons as baryonic particles.

Also, for what it's worth, it'd be possible to check one way or the other for several billion dollars worth of equipment: three large masses arranged in a scalene triangle with laser interferometers acting as a target plane, with another mass to target the plane at an angle of about 45 degrees relative to the face of the plane would either demonstrate a time base variance between the target masses -- or not. You have to keep the target masses relatively close to each other.

The speed limit on the mass after the slingshot would be about 240,000 KPH. To overcome that problem and get higher speed (we need relativistic speeds for crossing the plane), you need two more masses: one the size of the mass you sling-shotted, the other relatively smaller. From the reference frame of the large and small mass, the are effectively being dropped together onto a stationary object at 240,000 KPH. This will be enough to catapult the smaller mass up to relatavistic speeds for collision with the virtual plane. We don't care if the large slingshot mass and the large target mass survive, we just want the momentum transfer. Here's a nice little demo of the process: http://www.physics.org/interact/physics-to-go/extra-bounce/index.html [physics.org]

--Terry

Re:Actually, the referenced paper says something e (2)

bcrowell (177657) | more than 2 years ago | (#37029228)

They specifically talk about the LIGO II http://www.ligo.org/ [ligo.org] [ligo.org] gravity wave observatory. And yes, they believe that a gravity wave can be detected without having the ability to detect individual gravitons as baryonic particles.

Yes, and the existence of gravitational waves has already been proved indirectly by the Hulse-Taylor binary pulsar system, which is losing energy at exactly the rate predicted by general relativity. There is really no doubt about the existence of gravitational waves, either theoretically or empirically. LIGO is cool because it could open the door to a new way of doing astronomy, not because there is doubt about the existence of gravitational waves.

Re:Actually, the referenced paper says something e (1)

GNious (953874) | more than 2 years ago | (#37030728)

They specifically talk about the LIGO II http://www.ligo.org/ [ligo.org] gravity wave observatory. And yes, they believe that a gravity wave can be detected without having the ability to detect individual gravitons as baryonic particles.

Now my head hurts ... thanx

Re:Actually, the referenced paper says something e (1)

boristhespider (1678416) | more than 2 years ago | (#37031338)

Mine hurts too. The idea that we might detect gravitons as baryons is particularly painful.

Re:if black holes attract light (1)

bcrowell (177657) | more than 2 years ago | (#37029192)

hough some think the graviton is likely to be a tachyon (a particle that is faster than light.)

Complete nonsense. Please don't post garbage about topics you don't know anything about.

Re:if black holes attract light (0)

Anonymous Coward | more than 2 years ago | (#37030492)

hough some think the graviton is likely to be a tachyon (a particle that is faster than light.)

Complete nonsense. Please don't post garbage about topics you don't know anything about.

It does, in theory even though it is a hypothetical partical, move faster than light. See our allknowing encyclopaedia http://en.wikipedia.org/wiki/Tachyon

Re:if black holes attract light (2)

Ambitwistor (1041236) | more than 2 years ago | (#37031212)

The point is that gravitons are not tachyons. In all quantum theories of gravitation they're massless spin-2 particles, which travel at the speed of light.

Re:if black holes attract light (0)

Anonymous Coward | more than 2 years ago | (#37035188)

From which a question comes to mind : why would gravitons be capable of crossing from a universe to another in some marginal multiverse theories resting on NASA's dark flows..

Re:if black holes attract light (0)

Anonymous Coward | more than 2 years ago | (#37028216)

Light doesn't have mass so there is no force associated with attracting, or being attracted toward, anything at a distance. Light does however have momentum so if it impacts something it does exert a force on the object that it impacts (conservation of momentum).

What is actually going on it fairly non-intuitive and is not related to a force acting on anything. The extreme mass of the black hole is actually curving space such that a photon (or any particle) traveling on a straight path that passes through the event horizon of a black hole never leaves the black hole. In the reference frame of the photon, it is still moving in a straight line. However, in our reference frame it appears that it is orbiting, and falling into, the black hole - but there is no force acting on the photon to cause this orbit.

As for your last question: theory predicts that changes in the curvature of space due to massive things moving and/or spinning travel at the speed of light, which is the fastest we believe any information can be propagated. A lot of study has been done on this and the theorized "ripples" in space that propagate outward from two very massive bodies orbiting each other, such as two black holes orbiting each other, are actually really cool.

Re:if black holes attract light (1)

Ambitwistor (1041236) | more than 2 years ago | (#37028366)

Light has energy and energy creates a gravitational field just like mass does. Interestingly, momentum also creates a gravitational field (as does pressure). These are all aspects of stress-energy [wikipedia.org] .

It turns out that two parallel light beams in vacuum neither attract nor repel each other, because (in this special case) the gravitational attraction due to their energy is cancelled by a gravitational repulsion due to their momentum.

In general, light and matter attract each other.

Re:if black holes attract light (0)

Anonymous Coward | more than 2 years ago | (#37028724)

First off, black holes don't "attract light" (well, it does, but that's not what makes it black).
Black holes are black because the energy inside (light rays) do not have enough energy to escape the gravity well of the hole.
The light is BENT BACK by the extreme gravity.

Secondly, a "Light Beam" is basically a single photon (atom sized) oscillating through space (as a wave, with a point particle surfing it). So, Light has a tiny bit of electromagnetism that becomes a "beam" as it travels (at the speed of... wait for it... light). The gravitational influence of this point quanta is ... well, .00000000000000000000000000000000000001 (estimate) i.e. ... negligible.

Thirdly, gravity propagation is, like all, electromagnetic phenomenon an At the Speed Light phenomenon.

Current theories show that gravity is the 'closed' loop variety of string theory (as opposed to matter like electrons that are open strings attached to the M-Brane (space field). closed loops can cross over to other Branes which explain why gravity is so much weaker than the other forces (strong, weak, electromagnetic). Most of "gravity" as a force is simply not felt due to this ability to transfer out of our Brane.

Re:if black holes attract light (1)

tendrousbeastie (961038) | more than 2 years ago | (#37035644)

I was going to start with a hello to you, but have just noticed that you posted AC so I can't. Hello anyway.

First off, black holes don't "attract light" (well, it does, but that's not what makes it black).
Black holes are black because the energy inside (light rays) do not have enough energy to escape the gravity well of the hole.
The light is BENT BACK by the extreme gravity.

So the presence of the singularity causes the light to bend back towards it. In what way is the singularity not attracting the light? It is doing so indirectly by causing the local space-time to warp so much so that the light changes trajectory.

Secondly, a "Light Beam" is basically a single photon (atom sized) oscillating through space (as a wave, with a point particle surfing it). So, Light has a tiny bit of electromagnetism that becomes a "beam" as it travels (at the speed of... wait for it... light). The gravitational influence of this point quanta is ... well, .00000000000000000000000000000000000001 (estimate) i.e. ... negligible.

Well, given that photons are bosons and so can stack (aka a LASER) a 'beam' of light is not necessarily a single photon, but could be many. Plus the wave that represents the quantum mechanical w/p duality aspect (the Schrodinger wave) is a probability wave, not an EM wave.

Also, the energy of the photon is e = hf. Given that the usual quantisation factor for most Uncertainty Principle stuff is h (which I think is something like 1 time 10 to the minus 43) then the energy of a photon is at least f away from being negligible.

Thirdly, gravity propagation is, like all, electromagnetic phenomenon an At the Speed Light phenomenon.

It is c (3 times 10 to the 8). The "Speed of Light" implies a subjective assessment of how fast light moves in the medium one is currently occupying. Although, I have never read about what happens about gravity propagating in a non-vacuum, I assume it would still be c but who knows?

Current theories show that gravity is the 'closed' loop variety of string theory (as opposed to matter like electrons that are open strings attached to the M-Brane (space field). closed loops can cross over to other Branes which explain why gravity is so much weaker than the other forces (strong, weak, electromagnetic). Most of "gravity" as a force is simply not felt due to this ability to transfer out of our Brane.

When string theory makes any testable falsifiable prediction it will be allowed to 'show' things. At the moment it at best suggests. So far it relies too much on our assumption that our (meta)physical interpretations of a highly specialised form of maths represents an ontologically valid reality (especially when the Copenhagen QM interpretation pretty much did away with such ontologically relevant schemes and just went for modelling the data instead)

Not me (1, Informative)

Anonymous Coward | more than 2 years ago | (#37028134)

No, I didn't. Honest... I ran out of gas. I... I had a flat tire. I didn't have enough money for cab fare. My tux didn't come back from the cleaners. An old friend came in from out of town. Someone stole my car. There was an earthquake. A terrible flood. Locusts! IT WASN'T MY FAULT, I SWEAR TO GOD!

Disaster Alert! (1, Funny)

meburke (736645) | more than 2 years ago | (#37028536)

We at the Society for Extreme Alarmism take this opportunity to warn you of the impending end of the world! In only 12,000 years (Earth years, that is) the matter being sucked away from the blue star will cause it to explode. The same universal force that causes dropped toast to land butter-side-down will determine that this explosion will hurl the black hole on a direct collision course with Earth at about half the speed of light. Elementary mathematics proves that in only 24,000 years, then, a force more disruptive than Obamanomics will destroy the Earth!

Repent Now!

Re:Disaster Alert! (0)

Anonymous Coward | more than 2 years ago | (#37029810)

Lame.

Sounds familliar (2, Funny)

Anne_Nonymous (313852) | more than 2 years ago | (#37028694)

>> that result has inspired a forecast for the system's future: The black hole will swallow even more mass from an unfortunate star circling it

So basically, they're modeling based on our economy?

Re:Sounds familliar (0)

Anonymous Coward | more than 2 years ago | (#37029802)

>> that result has inspired a forecast for the system's future: The black hole will swallow even more mass from an unfortunate star circling it

So basically, they're modeling based on our economy?

lol

Sagittarius A* (4, Interesting)

bcrowell (177657) | more than 2 years ago | (#37028740)

You actually don't have to be a complete kook to doubt that solar-mass bodies like Cygnus X-1 are black holes. There are all kinds of other hypothesized objects that they could be, including black stars, gravastars, fuzzballs, quark stars, boson stars, and electroweak stars. These are all long-shots, but they exist in certain reasonably well-motivated physical theories.

For skeptics, I believe the evidence is stronger that Sagittarius A* is a black hole than that Cygnus X-1 is. Sag A* is the supermassive black hole at the center of our galaxy. Sag A* has been proved by indirect but very strong evidence [arxiv.org] to have an event horizon, which is essentially the defining characteristic of a black hole. (A singularity without an event horizon would be something different; the big bang singularity is an example of that.) It may become possible in the near future [arxiv.org] to do direct imaging of Sag A*'s event horizon, which would be direct proof that it's a black hole. There are fundamental reasons why we will never be able to do anything like that with any other black hole besides Sag A*, using foreseeable technology.

FTFY (1)

Anonymous Coward | more than 2 years ago | (#37029894)

Vag A* is the supermassive black hole at the center of our galaxy.

Re:Sagittarius A* (0)

Anonymous Coward | more than 2 years ago | (#37031016)

fuzzballs

In Germany, people play with those quite skillfully.

Exploding black hole? (1)

Lord Lode (1290856) | more than 2 years ago | (#37030772)

I thought nothing could escape a black hole, so how can it explode? An explosion requires escaping it. I'm asking this as a non-physicist :)

Re:Exploding black hole? (0)

Anonymous Coward | more than 2 years ago | (#37031110)

You are a victim of ambiguous English, it should say "when the companion, due to loss of mass explodes", the black hole may no longer be couples into the binary system and could make a slingshot escape. [Notice, Handwaving Deliberate].

Re:Exploding black hole? (1)

boristhespider (1678416) | more than 2 years ago | (#37031226)

They didn't say the black hole would explode, they said that the companion would.

Also, to answer the question you asked (even though it's not relevant here), a black hole won't "explode" but unless something's very wrong with our theories, it will dissipate. Black holes emit Hawking radiation, which you can view more or less as pair-production in the vicinity of an event horizon. Two quanta pop out of the vacuum; one falls into the hole, while the other escapes into the universe at large. The energy for that has to come from somewhere, and it comes from the event horizon. So the hole grows smaller as it emits Hawking radiation until ultimately (we assume) it vanishes.

Re:Exploding black hole? (1)

RockDoctor (15477) | more than 2 years ago | (#37032330)

Black holes emit Hawking radiation,

Well understood.

Now, to the extent of my knowledge, the black-body equivalent temperature of Hawking radiation is related in an inverse manner to the radius (or surface area, I suspect the latter for accuracy) of the black hole's event horizon, and the radius (surface area) is proportionally related to the energy content of the black hole.

So, when a black hole loses a quantum of energy via Hawking radiation, it's surface area/ radius decreases, and so the black-body temperature of the radiation will increase. As the black body temperature increases, on average the energy/quantum emitted increases, and the frequency between emissions increases.

So far, all so conventional. Hawking probably has his students do those lectures for the pre-school students.

But, as the black hole gets smaller, the energy per photon increases substantially. And eventually almost the last of the energy within the event horizon is going to go on the penultimate photon ... leaving a black hole which "wants" to spit out it's last photon at very high energy (with a vanishingly small probability of it emitting something at an energy as low as extreme-gamma, say), but it may not have sufficient energy to produce that photon.

How steeply cusped are the equations behind this? Is it possible that eventually a black hole wouldn't have enough energy to radiate at the frequency required by it's event horizon's curvature. Or do things get "fuzzy" when you're talking about quanta with wavelengths smaller than the Planck Length?

Probably related ... since high energy photons pack a lot of energy into a small wave packet ... and energy has mass (or what did you call it up-thread ... "it contributes to the space-time stress tensor", or somesuch) ... then a photon above a certain energy will have enough energy packed into a smalll enough volume, that it would be it's own black hole. No?

I asked a Fermilab physicist this once. I never did get a reply.

Re:Exploding black hole? (1)

Visserau (2433592) | more than 2 years ago | (#37033400)

I don't think the wavelength can go below the plank length. Photons have a fixed maximum energy that corresponds to that length. To release more energy more photons would be emitted instead of more energetic ones. If you could get smaller wavelengths (higher energy), presumably your photon would fall below the threshold of the uncertainty principle, and then I have NFI what would happen.

Also such a super energetic photon would not be a black hole - it exerts gravitational force yes, but a tiny one. Even assuming we managed to bump that up several orders of magnitude worth of "magical fudge factor", the force is negligible. Assuming anything else is around (e.g. this is occurring on earth) other forces (earth's gravity) would completely dominate any effect the photon could have.

(I can't believe we actually have to manually line break. Wtf?)

Re:Exploding black hole? (1)

Ambitwistor (1041236) | more than 2 years ago | (#37033942)

Basically, we don't know.

We don't know what happens when a black hole evaporates. That requires a theory of quantum gravity, which we don't have. Hawking radiation can be worked out in a semiclassical theory of gravity, so we know a black hole will shrink, but when you get down to "the last photon", we can't say what ultimately happens to the black hole.

Similarly, we don't know what would happen to a photon if you gave it Planck energy. That too requires a quantum theory of gravity. Below the Planck energy, it wouldn't form a black hole.

Re:Exploding black hole? (1)

boristhespider (1678416) | more than 2 years ago | (#37035204)

They're perfectly good questions - you just didn't get a reply because no-one knows the answers. Those would require a quantum theory of gravity, and we simply don't have one that's developed enough to answer such questions. For all we know, string theory is dead wrong and at a fundamental level all particles are little black holes that can't evaporate further. That seems unlikely, but until we have a working (and useful) theory of quantum gravity it can't be ruled out. (It's also basically useless as a supposition without being able to build a theory on it... which would still require quantum gravity.)

Re:Exploding black hole? (1)

RockDoctor (15477) | more than 2 years ago | (#37041894)

Oh goody, I like asking awkward questions, and I came up with this one out of whole cloth.

Old joke, you've probably heard it before:
Physicist is converted to "God" in some way shape or form. Physicist specialises in studying turbulence. Someone comments that physicist is likely to ask "God" to explain turbulence to him when he ascends to the Pearly Gates (Bills Cockney cousin?). "Oh, no," replies the newly-converted physicist, "I wouldn't want to embarrass the chap at a first meeting."

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