Perhaps the weirdest object in our universe is a black hole. Despite its peculiarity, it is extremely intriguing. Since its discovery in the 1970s it has been a red hot subject for astronomers. But what really is a black hole? What causes its creation? Such are the questions a keen mind asks. Most of us already have a concept that it is a hole in universe which sucks up and destroys everything, as this is the image which has been imprinted in our minds by the media and film industry. But the whole story is seldom told, and without a doubt, it is too interesting to omit.
Stars in our universe are made up of mostly hydrogen atoms which are constantly converting into helium atoms through fusion reactions. These reactions release a tremendous amount of energy through radiations. This energy is vital to maintain the normal shape of the star because the gravitational energy is constantly trying to shrink the star. The energy produced by the fusion reactions counters the gravitational energy and thus keeps a balance between the two forces. As a result, the shape of the star remains normal. But as these reactions proceed, the energy that prevents the star’s shrinking, depletes and the balance is disrupted. Gravitational energy wins and starts contracting the star .
Now the fate of the star depends upon its size. If the star has a core of mass less than 1.4 times the sun’s mass, the fusion reactions stop soon and the star compresses to a very hot ball—about the size of the earth—which we call a white dwarf. If the star’s core is between 1.4 to 2.8 times the sun’s mass, the star shrinks even more and becomes a neutron star having a circumference of 20 km. The neutron “soup” inside its core prevents more shrinking. But what if the core is of mass more than 2.8 times the sun’s mass? The star shrinks even more. But why does it shrink more? Why cannot the neutron soup resist it?
In smaller stars the reactions stop in the middle of the process. However in a star of humongous size they carry through the periodic table until they reach iron (Fe). Iron is different from the previous elements in the table. It forms through endothermic reaction (absorbing energy) whereas every other element went through exothermic reaction (releasing energy). As soon as iron reaches upper portion of the star, fusion energy depletes rapidly because it absorbs energy through formation. The balance between fusion energy & gravitational energy is disrupted & nothing is left to resist the gravity. Then, metaphorically speaking, in a blink of an eye, gravity of the star shrinks the whole star and every single atom is torn apart and a supernova takes place.
To comprehend the whole phenomena of black hole we must understand the concept of escape velocity. It is defined as the lowest velocity which a body must have in order to escape the gravitational attraction of a particular planet or other object. Earth has an escape velocity of 11 km/s, neutron star has an escape velocity of 150,000 km/s which is equivalent to the half of speed of light, and behold the fact that a black hole has an escape velocity greater than the speed of light. It means that in order to escape the pull of black hole one must be faster than light—and that is the problem. Nothing can even be equal to the speed of light let alone faster than it. That is why we call it black hole as it reflects no light. What we see is only an outline around it which we call event horizon (it is named so because whatever event takes place beyond it can not be known by us). Anything that crosses event horizon can never return and its fate is unknown to any human.
A black hole is practically impossible to approach. Most of the studies are purely theoretical about it. One of these theories is the theory of Spaghettification. When you stand upon the earth’s surface, the earth’s gravity acts on your feet slightly more than on your head but it is not felt by you because the earth’s gravity is not so high. But a black hole’s gravity is unimaginably high so you will feel it and your legs will be pulled faster than your head. Like spaghetti, you will become extremely thin and long, even reaching kilometers in length!
Now we must clear the misconception about black holes being a destroying machine. In fact, they are involved in the creation of stars and various elements. The dying star scatters elements such as calcium and silicon in the space and some of them go on to create stars. Some scientists even propose a theory that Big Bang was in fact a supernova explosion.
And so it appears that the true image of black holes is not of a villain but rather a hero. A black hole is not a destroyer but a creator. Wouldn’t it be wonderful if we could study everything deeply instead of believing in whatever the screens show?