Interpreting various equations from my limited knowledge of such a discussed area, I've come up with this:
Hawking radiation makes a black hole lose mass, hence diminishing its Schwarzchild radius. The Schwarzchild radius came up because it's a singularity (in the mathematical sense) in a solution to Einstein filed equations. The same way matter collapses onto itself up to creating such a singularity and being encompassed into the now existing event horizon, as soon as there is not enough mass to sustain the singularity, the event horizon vanishes, hence the remaining matter "pops" back into our sight.
You could view it otherwise with a thought experiment: take particles out of the black hole one by one. Each time it will reduce the mass and maybe the radius. At some point the mass/radius ratio may not be small enough to hold light and the bubble bursts in plain sight as the event horizon breaks down. In such a thought experiment, the worst case would be that the black hole would require every single particle but one to evaporate (unless you assume a single particle could be a black hole in itself).
An interesting back of the envelope calculation is computing the mass contained in a Schwartzchild radius of Planck length (the size at which quantum effects take over).
l_P = sqrt(hG/c^3)
r_s = 2Gm/c^2
hence m = sqrt(hc/4G) = 1.0882546265651108e-08 kg which is a bit more than 1e22 electrons sitting at a position 1e-15 smaller than a single one of them.
Is there anything to preclude there being an ultra-massive particle that might be able to cause a singularity by itself?
The particles we observe today exist in a relatively low-energy environment. Whatever's going on in the furious intensity that is the inside of a neutron star that's on the edge of becoming a black-hole could be quite spectacular in comparison.
Hawking radiation makes a black hole lose mass, hence diminishing its Schwarzchild radius. The Schwarzchild radius came up because it's a singularity (in the mathematical sense) in a solution to Einstein filed equations. The same way matter collapses onto itself up to creating such a singularity and being encompassed into the now existing event horizon, as soon as there is not enough mass to sustain the singularity, the event horizon vanishes, hence the remaining matter "pops" back into our sight.
You could view it otherwise with a thought experiment: take particles out of the black hole one by one. Each time it will reduce the mass and maybe the radius. At some point the mass/radius ratio may not be small enough to hold light and the bubble bursts in plain sight as the event horizon breaks down. In such a thought experiment, the worst case would be that the black hole would require every single particle but one to evaporate (unless you assume a single particle could be a black hole in itself).
An interesting back of the envelope calculation is computing the mass contained in a Schwartzchild radius of Planck length (the size at which quantum effects take over).
hence m = sqrt(hc/4G) = 1.0882546265651108e-08 kg which is a bit more than 1e22 electrons sitting at a position 1e-15 smaller than a single one of them.