A Black Hole is nothing more than a massive object with a huge density of matter and therefore a small size. This makes the gravitational field created by a Black Hole so large that it literally sucks in the surrounding matter and even prevents light from escaping from its surface. Multiple star systems have been observed with a black hole, whose presence is detected by the fact that it is losing matter from its companions. It is predicted that there is a black hole at the centre of our galaxy.
A black hole has a so-called event horizon, which is a spherical boundary around the black hole, but above its surface. If a particle crosses this boundary, it is doomed to never leave the black hole, and it moves inexorably towards its surface.
How does a black hole form?
It is most likely the last stage in the life of a massive star, which, after "burning out" fuel (primarily hydrogen, which is converted into helium) and upsetting the balance between its own gravity and the pressure resulting from thermonuclear transformations, begins to collapse into itself.
Because a black hole absorbs all matter and radiation that strays into its vicinity, this means that its mass is constantly increasing. This in turn amplifies the gravitational field it creates.
Such a scenario does not bode well for the universe - it means no less than that eventually all matter will be swallowed up by black holes, which will eventually swallow each other up, eventually ending up as a single black hole, which under the action of its own gravity will turn into a dimensionless point (because gravity also curves space-time).
This is one possible 'end of the world' on a cosmic scale. The other two scenarios arise from the fact that the universe is constantly expanding, and this leads to the question of what the dynamics of this process will be. Either it will expand indefinitely and we will end up in a cosmic desert, or the force of gravity will offset the "escape" of matter and the universe will be "frozen" and remain in this state indefinitely.
But it was supposed to be about evaporating black holes. Hawking did not like such objects that would devour the universe. He wondered if they were undergoing slimming therapy by emitting radiation. And he developed a model in which something like this actually happens. And this means that black holes are not so black after all.
In building his theory Hawking used the facts that there is a so called antimatter, and the interesting properties of vacuum, which as it turns out is not so empty after all. From a quantum mechanical point of view, a vacuum has a potential for the spontaneous existence of energy in the form of a virtual particle-antiparticle pair. Hawking compares such a vacuum to a bubbling cauldron of soup, on the surface of which bubbles - pairs of particles - briefly appear. The scientist assumed that such a pair appears on the event horizon, from which a particle of "ordinary" matter flies away and an antiparticle falls to the surface of the black hole. What does this mean? The antiparticle meets the particle-element of the black hole, this will annihilate both particles and lead to a shrinking of the black hole's well-being. The particle that was an element of the created pair is the so-called Hawking radiation. And at this point we come to the conclusion that indeed black holes need not be eternal objects, that they will eventually "evaporate".
The scientific output of Stephen Hawking is worth reading. We particularly recommend the book "A Brief History of Time".
