This animation illustrates the activity surrounding a black hole. While the matter that has passed the black hole's event horizon can't be seen, material swirling outside this threshold is accelerated to millions of degrees and radiates in X-rays. Image © CXC/A.Hobart
The radiation - Hawking radiation, does not come directly from the centre of a black hole. This electromagnetic radiation is ejected from the outside of the centre of a black hole, that is, from the region of the event horizon.
Related: Black Holes: How they work?
As the particle approach towards the event horizon, a virtual pair of that particle appears. Here, virtual particles were created by the perturbation in space and for this, the energy is supplied by the force of the black hole. Due to the tremendous force of black hole, one particle gets sucked into the gravitational pull of black hole and travel towards the centre of the black hole and one manages to escape from the event horizon or gravitational pull. Here, the virtual particle pair means the particle-antiparticle pair.
The general belief is that only anti-Matter/particle gets sucked and matter/particle gets escaped from the event horizon.
Now, an external observer would see particles being radiated out of the black hole but in fact, these particles are being created at nearly at the event horizon and they are not actually coming out of a black hole.
Because of this radiation, the black hole loses mass and so the smaller black hole will fade out on the cosmological time. In brief, this implies that a black hole loses mass to create a virtual particle.
Now at some point, particle-antiparticle pairs get detached and one will escape from the black hole and so the black hole loses mass generating radiation called Hawking radiation.
So far, you must be thinking of a question, 'Is Hawking radiation a proven thing or can be a proven thing?', I am.
Is Hawking Radiation Proven?
Hawking used the idea of entropy to describe an important and maybe the most revolutionary property of a black hole. The idea Stephen Hawking used was when a black hole absorbs new materials using its immense gravitational pull then the entropy of those falling materials must go on adding the overall entropy of black hole.
The entropy of materials that goes from outside of region called event horizon to the inside of the event horizon.
Till Stephens Hawking's theory of black hole radiation, scientists only know that the entropy is being added to the black hole and no-one knows if it goes infinitely adding or it would be ejected from the other side of the black hole. Hawking claimed that this entropy can not go on adding like this and there must exist a balance.
The idea was a black hole must also eject some forms of matters or particle that should balance the added entropy. So he introduced the idea of ejection of entropy by black holes in the form of radiations which we now called Hawking radiation. He also mathematically calculated the value of entropy and theoretically solved the entropy problem of black holes.
Regarding the visualization of Hawking radiation, Hawking radiation has never been observed significantly. The main obstacle causing hinder in observing this radiation is the mass of black holes.
Till now we have evidence the black holes with lots of hot particles/matter falling into it and due to the radiation of copious infall of particles and matter, the tiny Hawking Radiation effect is completely smothered.
Hawking calculated that for a black hole of M solar mass, it should radiate like a blackbody of the temperature of 6 × 10-8/M Kelvins which is a small quantity. So, for very small black holes encompassing relatively less particle/matter into it will have a more significant value of this radiation, and scientists are in a dilemma whether such a small mass black holes may have existed from the gravitational collapse of greater mass black holes.
If black holes evaporate under Hawking radiation, a black hole of mass of about solar mass will evaporate over 1064 years and a supermassive black hole with a mass of 1011 M☉(M☉being solar mass) will evaporate in around 2×10100 years. By prediction, some monster black holes in the universe are to continue to grow up to perhaps 1014 M☉and would evaporate over a timescale of up to 10106 years.