"Black Holes Ain't So Black!"
English physicist Stephen Hawking has suggested that radiation might not only exist near the black hole, but that it might actually be leaking from the black hole itself. Can energy really leak from a black hole? It sounds impossible from all we've learned so far!
Hawking suggested that the source of this radiation is what are called "virtual particles." These particles do not obey the regular laws of physics. They can be created in pairs out of nothing, contrary to the normal laws of physics. As pairs, they can then collide with one another and be destroyed back into empty space. Normally, we would therefore never even see these particles before they disappear.
Hawking theorized that if a pair were created right at the event horizon of the black hole, then one particle of the pair could be sucked into the hole while the other escaped outward.
The result to an outside observer would be to see a new particle arrive that appears to be coming from the black hole. Hawking proposed that the resulting stream of these particles, which were photons, would then look like radiation coming from the black hole, an effect that came to be called "Hawking radiation."
So in fact, black holes, which were thought to emit no radiation all (which is why they are called "black" holes), in actuality give off a small amount of light! In Hawking's words, "Black holes ain't so black!"
Black Hole Explosions
As a black hole loses energy, it is in effect losing its mass as well, since Einstein showed in his famous equation below that energy and mass are interchangeable. Hawking's theory suggests that there might come a time when a black hole has lost so much mass that it will no longer be able to completely curve the space surrounding it enough to completely contain its light.
It would therefore no longer be a black hole. Hawking predicts that, at this point in time, the black hole would explode outward with a force equal to millions of hydrogen bombs!
But don't look up in the sky and expect to see a fantastic display of fireworks, all coming from exploding black holes. A large black hole is predicted to last a long, long time, longer by far than the age of the universe (which is around 10 to 20 billion years!). It would take trillions of years for the black hole to lose enough mass for it to explode.
Don't expect to see a grand fireworks show coming from exploding black holes any time soon.
Yet it may be possible that mini primordial black holes created in the Big Bang might be exploding just about now, releasing energy in the form of intense gamma rays (electromagnetic radiation similar to x-rays, only with much more energy), equal to almost 1 million volts of electricity.