We all have stumbled across the term ‘black hole’ but we have never really got past the fact that Stephen Hawking has made significant discoveries about them. Indeed that is true, but here we will try to understand the essence of black holes and all the rumors about them which have attracted the attention of great physicists and cosmologists around the world. The existence of black holes was discovered not a long time ago and since that time we have acquired a fairly good understanding about their structure and their properties. The reason why black holes are really popular in the science community because they hold the possibility of answering questions about the creation of our universe and also about the existence of ‘multiverse’. A multiverse refers to other universes which may or may not have properties or the laws of physics which are applicable in our own universe.
A black hole is referred to as a region of space-time which has very strong gravity. So strong that even light cannot escape its gravitational pull. That is why, it is almost impossible to visually record the existence of black holes in a galaxy.
How are they formed?
There are stars in our universe that are way bigger than our sun. These are probably hundreds of thousands of times bigger and these eventually form black holes. According to the law of gravitation, the gravitational force exerted by a body is proportional to its mass. Since the mass of such stars reaches gargantuan proportions, it can be concluded that these stars have very strong gravitational fields. In the core of these stars, nuclear fusion takes place. This involves the release of light and heat which make the star glow. Now, each star has a cycle. At the end of the cycle, the fuel causing the nuclear fusion reactions in the core gets exhausted and the star begins to die. Due to the exhaustion of the fuel and the strong gravitational pull which acts inwards, the star begins to contract reduces to a very small size. This contraction causes the core of the star to become extremely dense and extremely hot. Due to this instability, the star explodes into a supernova. A supernova is the explosion caused at the end of the cycle of a star which results into an outburst of radiation, gases and the materials of the star. Only the core remains following the events of the death of the star. This core is infinitely dense and tremendously massive and has very strong gravitational pull. This core is called ‘singularity’ and the vicinity of the core is called ‘event horizon’. Together, these constitute a black hole.
The mass of a black hole is very large. Black holes can be millions or even billions of times more massive than our sun. There are a large number (maybe billions) of black holes in the universe. It has been theorized that there exists a black hole at the centre of every galaxy, including our own Milky Way.
Once they are formed, they are not confined to their original size. They continue to grow by absorbing the matter around them like cosmic dust. Since their gravitational fields attract everything around them, it is speculated that when multiple number of black holes come closer, they merge together to form a bigger black hole.
Some physicists go so far as to say that black holes are portals into other universes. If this is true, then we have to acknowledge the possibility that our universe might have been originated from a black hole of some other universe.
What exists inside a black hole is still unknown. But whenever an object falls into a black hole near the singularity, it is sucked spirally into the black hole due to the strong gravitational pull. Due to this, the object gets heated up to millions of Kelvin and emits X-rays. It is by the virtue of these emitted x-rays that we come to know about the existence of the black holes.
They have also been linked with time travel and worm holes and remain fascinating objects in the universe.