Hi so.

the death of a black hole is a complicated thing. and whether a black hole dies, and the details of it, will depend on how complicated/quantum mechanical the theory is. there are three levels of quantum complexity.

- general relativity (no quantum matter)
- matter with quantum properties in a classical general relativity context
- quantum gravity

the deal is, I'm sure you have heard, that quantum mechanics and einstein's theory of general relativity don't play well together.

They are not friends at all.

Einstein's theory is a classical one (no quantum matter) but it's one where "the curvature of spacetime (gravity) tells matter how to move, and the motion of matter tells spacetime how to bend".

because of this, your hands are kind of tied if you want to introduce quantum mechanical matter. because of it's quantum nature, we don't know exactly how it bends spacetime.

but. what you can do is make models where the quantum mechanical matter doesn't really weigh enough to bend the spacetime, and ask "what effect does the curvature of spacetime have on the quantum matter?" (so, it's not a *proper* gravitational model, because we assume that the quantum matter has no gravitational effect).

if you put a quantum field around a black hole, you find something strange. If you drop a particle detector (like a geiger counter) into a black hole and it might say "there is no radiation". but If you take another particle detector and hold it at a constant radius (holding it against the pull of gravity), it will say "there is lots of radiation". this radiation is called Hawking Radiation. there is a related type of radiation called "Unruh Radiation" which is seen by accelerating spaceships even in spacetimes with no curvature.

anyway. Hawking has a good explanation for what's happening. quantum mechanics, imaginary particle-antiparticle pairs are always popping in and out of existence. If this happens near an event horizon, one of the particles can fall into the black hole, and the other will hang out outside the black hole: giving us a bath of radiation.

In hawking's explanation, the energy used to create the particle that doesn't get swallowed ends up being subtracted from the black hole.

so is the radiation "real"? is it somehow connected to the matter that fell into the black hole? does the black hole actually lose mass as a result of hawking radiation?

no one knows the answers to these questions. obviously, the realness of hawking radiation depends on how tongue-in-cheek you are willing to be with the whole "the quantum matter doesn't gravitate" argument we required to start the calculation. It is a field of active research, and you might hear people

talking about firewalls. this is what they are discussing.

So. one question we might want the answer to is "how bright is the hawking radiation/how intense is the energy?" and the answer is that it depends on how small the black hole is. the smallest black holes radiate most strongly.

So really big black holes (like the ones at the center of the galaxy) are "stable", in that they don't radiate very much hawking radiation. Really small black holes (like, if one was made by CERN) are "unstable", in that we would expect them to radiate away their own mass really quickly using this hawking radiation mechanism.

so what's the truth? I'm afraid that until we have a good theory of quantum gravity, we will never know exactly how the emission of quantum particles affects the mass of a black hole