Yashika Jain
The universe is one of the most mysterious places ever known. A lot of decades have passed since we are studying it; still, we are unable to disclose all the secrets of it. Among various objects in outer space; there is one named black hole.
Black holes are very arcane. These are objects having leaden mass in contrast to their small size. Their gravitational pull is so strong that nothing can pass through it, not even light.
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Types of Black Holes
There are 4 types of black holes.
1. Stellar Black Holes
Dying stars lead to the formation of black holes. Inside it, the nuclear fuel and its gravity collide lead to its stability. When its nuclear fuel vanishes, gravity compresses the star. In this way, a black hole is created.
This only happens in big stars at least 10 times massive than the sun. These are the most common types among others. Our Milky Way galaxy also has a variety of these black holes.
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2. Intermediate Black Holes
As its name suggests, it cannot be formed from a single star. According to astronomers, these are formed maybe by a black hole engulfing a lot of material or when two black holes merge. But they are not sure about the cause. Their mass lies between 100 and 1000 solar masses. (1 solar mass refers to the mass of the sun.)
3. Supermassive Black Holes
The theory regarding their formation has not been confirmed yet. These are the largest and heaviest black holes among others.
They are present at the center of every galaxy. Our Milky Way galaxy also has ‘Sagittarius A+’: a supermassive black hole at its center. Their mass lies between millions to billions of solar masses.
It is said that may be due to their presence in the center of the galaxy containing billions of stars and heavy dust they acquire such mass over time.
4. Miniature Black Holes
According to scientists, these black holes formed during the big bang. They are 60 billion years old. Their event horizon is comparable to atomic particles. These black holes are compressed to such a small point that they explode into massive explosions one day.
Escape Velocity and Event Horizon
Escape velocity is the velocity required by an object to reach the safe zone from a black hole’s gravitational pull. The escape velocity is given as:
$V_{e}=\sqrt{\frac{2GM}{R}}$
Derivation of Escape velocity in Newtonian gravity:
$\frac{1}{2}mV_{e}^{2}=\frac{GmM}{R}$
$\frac{1}{2}V_{e}^{2}=\frac{GM}{R}$
$V_{e}=\sqrt{\frac{2GM}{R}}$
The event horizon of the black hole is equivalent to the set of points around it. Its escape velocity is equal to the speed of light i.e. 299,000 km/s.
Sun Vs Black Hole
Fortunately, our sun does not have enough mass to become a black hole. After 4 billion years, our sun’s nuclear fuel will get vanishes and it will die or eventually become a white dwarf.
As a matter of fact, even if a black hole ends up taking the place of our sun. Our Earth remains at its position, considering that the gravity of it will be the same as that of our sun. So, all planets will revolve around that black hole like they now do so around our sun.
What Happens to Time Inside a Black Hole?
According to Einstein’s theory of relativity: high the speed of the object; slow the time will pass. At the event horizon, the object rotates with such high speed that times slow down to such an extent that it seems to have stopped.
Due to this the object falling into it also seems to have frozen. According to various theories, we can time travel through a black hole as inside a black hole time travels in 3 forms i.e. present, past, and future.
Hawking Radiation
Famous scientists Stephen Hawking predicted that black holes actually emit radiations, which he named ‘Hawking radiation’. These radiations also are known as ‘black body radiations’.
They reduce the mass of the black hole which leads to slowly shrinking of it and eventually lead to its evaporation; also known as ‘black hole evaporation’.
Death of a Black Hole
Black holes are the heaviest object in the universe. It is so much heavy, that all the physics laws break around it. Due to Hawking radiation, their life is finite.
Albeit, their life is finite and they will die or technically say, evaporate one day. Yet, they will take more time than the current age of the universe to completely disappear.
Summing it up it can be said that the black holes are the things open for research. They are still hiding many interesting secrets in their core.
Even, some of the mentioned theories are just predictions or assumptions of scientists; despite their arduous efforts they are not able to find proves in confirmation regarding this.
Waiting for new technology and new things to uncover before us. (God bless!)
