Hawking radiation (S.W. Hawking; 1973):
Black holes emit radiation such as any other hot body. Virtual particle-antiparticle pairs are being formed in supposedly empty space constantly. Sporadically, a pair will be formed just outside the event horizon of a black hole. There are three possibilities which are following:
a) both of the particles are captured by the hole;
b) both of the particles escape the hole;
c) one particle escapes whereas the other is captured.
The first two cases are simple; the virtual particle-antiparticle pair recombines and returns their energy back to the void by the uncertainty principle.
It is the third case which interests us. In this case, one of the particles has escaped (speeding away to infinity), whereas the other has been captured through the hole. The escapee becomes real and now can be detected through distant observers. However the captured particle is virtual still; due to this, it ought to restore conservation of energy through assigning itself a negative mass-energy. As the hole has absorbed it, the hole loses mass and therefore appears to shrink. From a distance, it seems as if the hole has emitted a particle and decrease in mass.
The rate of power emission is proportional to the inverse square of the mass of hole; therefore, the smaller a hole gets the faster & faster it emits Hawking radiation. It leads to a runaway procedure; what happens while the hole gets extremely small is unclear; quantum theory appears to indicate that some sort of "remnant" might be left behind after the hole has emitted away all its mass-energy.