Facts About Black Holes
Physics and astronomy deal mostly with things that can be seen, or that can be "felt" with the help of special probes, however black hoes are entities that one can neither feel nor probe so far. That is because black holes are bodies that are supposed to absorb everything that reaches them, including the probes using which we might try to see or feel them. So much so that even rays of light that fall upon it are absorbed and you cannot see them. Their presence is deduced from their effect upon astronomical objects and also from mass-calculation of mega star-clusters.
Formation Of Black Hole: It seems that black form by the collapse of stars. Stars can collapse when their mass is so high that their internal gravitation attraction exceeds the forces that keep the star in a normal state. This can happen when the star is unable to maintain high heat, and thus a rarefied form. This can also happen if too much external mass is absorbed by a star so that the new mass creates a gravitational force that exceeds the forces that were able to maintain the star in its earlier form.
Once a star begins to collapse towards its center due to gravitational forces, the process only accelerates. That is because the more dense it becomes, the more the gravitational attraction and the more the collapse. Thus a chain of self-perpetuating events is set in motion where the process continues till it reaches some sort of equilibrium. This state is called a black hole because objects that approach close to it are swallowed up, increasing its mass further, and increasing the forces that started the collapse in the first place. This attraction is so strong that all external light that falls upon it is absorbed and therefore one cannot see the black hole. What is more, any light produced inside the hole cannot escape its gravitational pull anymore and the black hole seemingly is confined in self-created darkness forever.
Theoretical studies have shown that black holes can also be created if two high-energy particles collide to make a structure that has a density high enough to create gravitational forces similar to that of the black holes. These theoretical predictions have been put to test in high energy particle accelerators but the results are negative so far. This means that far greater energies of collision will be needed for the formation of such collisional black holes, assuming that the theory is right, The main problem here is that researchers are dealing with an entity that is beyond observation and that is unlike anything else in the Universe. So much so that even many physical laws break down inside and in the vicinity of black holes.
The Future Of Black Holes: The peculiar nature of black holes makes them difficult to study, but it is clear by now that the laws of conservation of mass and energy do not break down in them. This means that black holes will continue to exist indefinitely, and that they will not vanish or become extinct. However, they can definitely interact with other bodies during this period absorbing a lot more of them. It seems that they can also form a twin body system with a normal star or with another black hole. Attempts are going on to search for such twin systems as their interaction can give unusual insights to scientists about black holes.
It also seems that some black holes will have plenty of "free" matter around them so that that they can keep on devouring matter external to them for millions of years. Each time that this happens, its mass increases further and the radius of the region from which it can now pull bodies into itself increases further.
There has been some theoretical speculation in recent times that predicts that in spite of the tremendous inward gravitational pull, at least some black holes might emit an extremely weak form of radiation labelled Hawking radiation. The predicted intensity of this radiation is so weak that there is no way to detect it from the earth even if the prediction is right. Extremely sensitive, special purpose, space-based telescopes might detect them sometimes in future.
Summary: At present black holes continue to be enigmatic bodies that are known more because of theoretical studies and less because of any direct observation. The situation might change in future with new breakthroughs in theory or with new discoveries in lab or in space.