Where does the mass go in a Black Hole?

[Tabash36]

The mass that is captured by a black hole, what happens to it?

Do black holes continue to 'grow' along with the amount of mass they 'ingest'?

I'm curious if there are hypotheses about the 'fate' of the mass and energy trapped by a black hole. Could there be a point at which the amount of energy and mass contained in a black hole reaches a threshold where it is no longer a black hole?

[antoniseb]

Could there be a point at which the amount of energy and mass contained in a black hole reaches a threshold where it is no longer a black hole?

As we currently understand things, the entire mass of the universe could all be put into one black hole, and it would still be a black hole.

[Cougar]

The mass that is captured by a black hole, what happens to it?

It continues to affect the surrounding area via its gravitation. In colloquial terms, it gets spaghettified as it nears the singularity. General Relativity apparently demands a singularity, but I think this just means that GR breaks down at that point, with quantum gravity taking over. However, nobody has figured out quantum gravity yet. So we don't know what happens to mass as it hits the singularity.

Do black holes continue to 'grow' along with the amount of mass they 'ingest'?

Yes. If there is no longer any local mass (or significant radiation) to accrete, they will very, very slowly evaporate via a process involving Hawking radiation.

Could there be a point at which the amount of energy and mass contained in a black hole reaches a threshold where it is no longer a black hole?

As Antoniseb notes, the answer is very likely "no." Historically, the more crucial question was, "How massive must a collapsing star be so that it results in a black hole?" The solution was kind of tricky since a lot of the star's mass gets blown off into space in the process.

[Tabash36]

Thank you for the replies so far. Definitely some intellectually stimulating mysteries surrounding black holes.

A few follow-up questions if I may.

What is Hawking Radiation?

The singularity, or proposed singularity of a black hole, is itself a very dense mass? Having been born out of the collapse of a star, thus representing a portion of the original star's mass, given that much of the original mass was 'blown off' in the formation process, is my understanding here correct?

And, if the entire mass of the universe could be put into a black hole, and it still remain a black hole, how does this fit with the big bang theory? Or, is it that the conditions of the universe's formation were such that the big bang resulted, rather than a collapse toward a singularity?

And, what would current theories postualte the outcome would be if 2 black holes were to come into contact?

[max8166]

What is Hawking Radiation?

Professor Stephen Hawking of Cambridge Univesity England (http://en.wikipedia.org/wiki/Stephen_Hawking)
Devised a theory in which a Black Hole could evaporate. IMO a simplifcation of the theory is that particles are continually being created and destroyed in the vacuum of space, the particles always appear in pairs, one particle and one anti particle. He believes that should such an occurance happen on the event horizon of a Black Hole then the anti particle could annilate mass in the Singularity whilst the particle could be ejected from the vicinity on the Black Hole. More Depth here http://en.wikipedia.org/wiki/Hawking_Radiation

[Tabash36]

Thank you for linking the site with the information regarding Hawking Radiation.

Given the theory, would it be correct to then postulate a black hole of a size that is stable? That is one that has a gravitational force strong enough to capture the radiation that is formed at its boundary.

Also, I suppose one could then postulate a black hole of sufficient size that captures more energy than it releases (or is apparently released), therby 'growing' in size and presumably gravitational strength.

[Peter Wilson]

All black holes are thought to be growing in size/mass.

Very small BHs can evaporate, but any small enough to do so would have done so a long time ago.

[JohnD]

Tabash,
Mass bends space - that is general relativity (I think)
A black hole is a singularity, where all the rules of our universe break down, because the enormous mass bends space to such an extent that GR cannot predict what happens.
Outside the singularity is the event horizon, a surface where anything, including light cannot leave the BH. This is the place where Hawking radiation is supposed to occur, as the virtual pairs of particles, that quantum theory predicts and that normally rejoin again in an instant, are seperated, one going through the EH into the BH, one escaping into the Universe.

The rate at which this happens depends on the size of the BH. A small BH will have a small radius EH, which will allow more Hawking radiation to escape. The larger the BH the less Hawking, but there is always hawking radiation, because even an EH that was a flat plane would still release some.
So a black hole can never be so large that it will have "a gravitational force strong enough to capture the radiation that is formed at its boundary". However the bigger the BH, the less are the tidal and other effects near the EH. And it has been suggested that our Universe exists INSIDE a Black Hole!

John

[Dragon Star]

Very small BHs can evaporate, but any small enough to do so would have done so a long time ago.

I'm under the impression that all BH's will evaporate in time. (though it would take quite a while for this to happen to a SMBH.)

[Doodler]

As we currently understand things, the entire mass of the universe could all be put into one black hole, and it would still be a black hole.

A very BIG blackhole. With no real clue whats under the horizon, you could have anything from a monstrously dense star to a pinprick of matter at the very center of the event horizon. I'm personally in the incredibly dense/yet still sizeable camp.

Something as massive as Sag A* in the center of the Milky Way is around the 2-3 million solar mass mark with an event horizon an AU or two across. The more mass you feed it, the bigger the horizon gets, so something is there and accumulating matter. As to whether its a pinprick singularity or a crushed neutron star composed of charge balanced quarks instead of subatomic particles, or whatever. Something's in there.

[eburacum45]

I'm under the impression that all BH's will evaporate in time. (though it would take quite a while for this to happen to a SMBH.)

The difference is that Supermassive Black Holes (SMBH) and even stellar mass BH are 'cold'; that is they emit Hawking radiation at such a low rate that their effective temperature is lower than the Cosmic Microwave Background Radiation (CMBR). That means that these black holes absorb energy from the CMBR, and so are growing all the time.
Eventually, when the CMBR is redshifted so much that it is colder than the black hole temperature, the holes will start to lose energy, and eventually evaporate.

[Tabash36]

A black hole is a singularity, where all the rules of our universe break down, because the enormous mass bends space to such an extent that GR cannot predict what happens.
John

So, then GR is as close as we have come yet in understanding what is happening, but admittedly isn't the whole enchilada. There are still some 'holes' in our understanding.

And it has been suggested that our Universe exists INSIDE a Black Hole!
John

So, we may have black holes inside of a black hole? Intriguing!


I guess a lot of my questions arise from trying to consolidate the Laws of Conservation of Mass and Energy with the events surrounding a Black Hole. Of course, if the rules don't apply, then that becomes a fairly intractable problem to deal with.

Assuming the fundamental Laws do apply on a cosmic scale, if the total amount of 'stuff' in the Universe is a constant, then is there some sort of cosmic equilibrium with Black Holes playing their part in the cycle of mass/energy?
Or, what is thought happens to the 'stuff' that is released from a BH eveporation? What happens to the non-virtual particle from Hawking Radiation?

Thanks again for all of the input, it is greatly appreciated.

[JohnD]

Tabash,
Cosmic equilibrium? Metaphysics! The 'stuff' is still there, it doesn't re-appear in a white hole somewhere else, of the BH would lose mass by some unseen route.

DH,
You don't need to have a supermassive BH for it to take while to evaporate.
A Black Hole with the mass of our sun would take 67 BILLION years to disappear. If you want to calculate how long a smaller BH will take, see the Wikipedia: http://en.wikipedia.org/wiki/Hawking...le_evaporation

John

[Spacer X]

A very BIG blackhole. With no real clue whats under the horizon, you could have anything from a monstrously dense star to a pinprick of matter at the very center of the event horizon. I'm personally in the incredibly dense/yet still sizeable camp.

Something as massive as Sag A* in the center of the Milky Way is around the 2-3 million solar mass mark with an event horizon an AU or two across. The more mass you feed it, the bigger the horizon gets, so something is there and accumulating matter. As to whether its a pinprick singularity or a crushed neutron star composed of charge balanced quarks instead of subatomic particles, or whatever. Something's in there.

You've basically answered my question that I'd wanted to ask on this forum.
But you know a good answer creates more... Questions

I'm interested in black holes and I'm crazily curious what hides beneath the Event Horizon

I learned from your post that:
- what is beneath the Event Horizon is currently uknnown to people but there must be some theories speculating what may be there? You've mentioned about the singularity and quark star theories. Isn't it possible to count the number of quarks supposedly residing inside the EH and to weigh them and come up with an outcome linking the radius of a black hole it should have with a mass and volume that this probable quark star needed? It would then be possible to compare it with observational data (since we know correctly the radii of black holes or rather EH) and provide a scientific result approving/disproving this idea?

- In the case of singularity : is EH just a barrier for us to see more and any matter passing this point is continuing the travel into the singularity point?
So if there is a singularity point indeed why the relation more mass bigger radius of EH exist? There shouldn't be such connection I dare to say irrespective of the amount of the matter going to that point?
And a question related :
- Are quarks currently believed to be the smallest subparticles/bricks building atoms? What are smallest in size sub/particles known?
Thank you in advance for your Answers

[Jeff Root]

Hello, Spacer X!

You are right that the event horizon of a black hole is just
the limit of how far we can see. Anything which falls into a
black hole continues to fall toward the center. In fact, unless
there is some force which can stop it (which there is absolutely
no indication of), matter will fall toward the center forever.
Even though it is accelerating as it falls, increasing speed
toward the center and away from the universe outside, because
of the strange shape of spacetime inside (and around) a black
hole, the matter never reaches the center. It is as though the
hole is constantly getting deeper, as the original star which
collapsed to create the black hole becomes ever denser, making
the gravity field at the center of the black hole ever more
intense. So the matter inside a black hole is not infinitely
dense-- it is not all concentrated into a mathematical point--
but it is always and forever approaching infinite density and
"singularity" more and more closely.

The size of the event horizon depends directly on the black
hole's mass. The greater the mass, the larger the volume of
spacetime which is sufficiently warped to prevent light from
escaping.

The concept of "size" when applied to subatomic particles is
absurdly complex. However, in simple language, basically yes,
quarks are the "smallest" constituents of matter, along with
gluons, electrons, neutrinos, and photons. They are pretty
theoretical in nature, since they can never be observed
directly (according to the theory!), but the theory works very
well in describing the behavior of the particles that quarks
and gluons comprise, so in every sense I'd say that they really
do exist.

-- Jeff, in Minneapolis

[Spacer X]

Thank you Jeff for your answers.
You especially helped me to understand that counting and calculating mass of anything and especially of such untouchable particles as quarks (which have other properties than ordinary macro-scale things which have easily desciptive mass and volume they occupy) is out the question (or close to) in light of quantum theory and especially so inside the gravity well of BH where curvature of space makes everything so complicated to calculate and measure.
Yes that was not wise to expect scientists to count and weigh quarks inside a BH.
Well thanks to your explanations and others that I've read in this forum I imagine that a black hole is neither a quark star or a singularity point. More something in between.
It is a shredded matter incessantly and indefinitely travelling towards the center of gravity - the abovementioned Singularity which is only an abstract notion since the matter when is going closer to it the gravity well collapses more and the matter does not reach the SP.
May I call it the incessant neverending travel of matter and energy towards escaping well center ?