The Fate of the First Known Black Hole 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."
It's Coming this way! (Score:1)
Run for your lives!
it's coming right at us! (Score:2)
get your guns out, people...
There's an important lesson for physicists in this (Score:3, Funny)
Never, ever, EVER bet against Rush. [wikipedia.org] Ever.
Steven Hawking, [techie-buzz.com] I'm looking at you.
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I think Steven Hawking's Speak and Spell should be auto tuned to Geddy Lee's High Falshetto.....
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someone needs to redub Hawking's lines in this then
http://www.youtube.com/watch?v=zSgiXGELjbc [youtube.com]
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Infinity, the star that would not die
All who dare to cross her course
Are swallowed by a fearsome force
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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.
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So... if they were right about that... what does that mean for us in 101 years time?
Meme (Score:1)
I for one welcome our new gravitational overlord.
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We already welcomed YO MAMA!
Little Known Fact (Score:1)
The mound is the hole's only natural enemy.
if black holes attract light (Score:3)
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?
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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.
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"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.
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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 (Score:5, Informative)
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.
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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.
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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.
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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.
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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
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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 Ene
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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.
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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
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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 ma
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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. (Photon
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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!
Actually, the referenced paper says something else (Score:3)
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 ano
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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.
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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
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Mine hurts too. The idea that we might detect gravitons as baryons is particularly painful.
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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.
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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.
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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.
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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?
Not me (Score:1, Informative)
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!
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Yes! Yes! Jesus H. tap-dancing Christ... I HAVE SEEN THE LIGHT!
Disaster Alert! (Score:2, Funny)
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
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Sounds familliar (Score:2, Funny)
>> 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?
Sagittarius A* (Score:5, Interesting)
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 (Score:1)
Exploding black hole? (Score:2)
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 :)
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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 tha
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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 temp
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Also such a super energetic photon would not be a black hole - it exerts gravitational force yes, but a tiny one. Eve
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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 ene
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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 sup
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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."