Black Hole- A myth till now, A mystery yet to reveal.


Thank you very much friends for your encouraging response to my last post about  Space Pollution: Speed Breaker for Future Space Programs.

I hope, you will enjoy the reading about the black hole also. Let's get started...


Black hole- a myth till now, a mystery yet to reveal. On 10 April 2019, by a team of International Astronomers, first ever real black hole image was captured by using Event Horizon Telescope (EHT).
Stephan Hockings, Einstein and other world-famous physicist were predicted the existence of black hole (and eventual a white hole) in late 20th century. But that was on paper, with the help of some equations and assumption.

Actual M87 black hole image taken by Event Horizon Telescope

But on 10th April, 21st century’s scientist proved their theory right and brought justice to their life ling study.

But what is actually black hole? is it just a hole in a space? How does it come into existence? If we can not see it then how could scientist discovered the M87 galaxy’s core where black hole exists.

Please allow me to answer your questions one by one.

1.     What is black hole?

2.     How does it come into existences?

3.     How could scientist discovered it if we can’t see it?

 

1. What is black hole?

 
Most accurate, computer generated black hole image from the Hollywood movie Interstellar

Black hole is astrological concept (till now) which defines itself as a place in space where at very small area, huge mass is concentrated and causing tremendous gravitational pull. That gravitational pull cannot even allow the light to escape form it. So, the escape velocity for area is more than the speed of light (300,000 km per second approx.). 

 

2. How does it come into existences?

 

Black hole is formed by the death of any star, means when a star dies then it will become black hole with time. But the question is ‘could any star become black hole after his death?’ Well the answer is NO.

If a star is about to die (Star dies means the gases fuel it is containing, is about to finish) and his mass is less than 1.4 times of mass of our sun then it will end by becoming white dwarf.

If the mass of dying star is in between 1.4 to 3 times the mass of our sun then it will become neutron star.

And if the mass of dying start is more than 3 times the mass of sun the it will become black hole. This is called as ‘Chandrashekhar Limit’. He had been awarded with Noble Prize for his equation.
 
Chandrasekhar Subrahmanyan- Inventor of Chandrasekhar Limit

There is the force generated at star’s core due to nuclear reaction which is directed away from the core and there is the gravitational force which is directed towards the star’s core. When the star has sufficient amount of fuel, these forces are balanced and keep the star stable and alive.
 
When the star is about to die, the gravitational force becomes stronger than force generated due to nuclear reaction. So, that gravitational force starts to pull the star mass at its core, start to literally crush the star. More the star mass starts to concentrate at the core, stronger the gravitational pull becomes. At the end, the whole star mass gets concentrated at very small space which makes it most dense object in the universe called as black. It is so dense that even light which is emitted by the star, cannot escape from its gravitational pull. So, if there is no light, we can not see it. That’s why human cannot see the physical appearance of black hole.
 
But here, new question arises ‘there must a limit till where the black hole’s gravity affects the light?
 
Well the answer was given by Karl Schwarzschild in 1916. In simple words, if defines as the distance within which the black hole has control over the light and light can not escape. If the light is beyond that distance then it can escape the blockhole’s gravity. This is called as ‘Schwarzschild Radius’.

Schwarzschild Radius =    2*G*M
                                       ---------------
                                               C2

Where, G- Universal Gravitational Constant

            M- Mass of Star

            C- Speed of light
 
Karl Schwarzschild

Let’s take an example of our own star ‘The Sun’. Its radius is about 700,000 km. Suppose our sun becomes black hole then its Schwarzschild Radius will be 3 km only. Suppose our earth becomes black hole the its Schwarzschild Radius will be not more than 1 cm (Strange, isn’t it?). Means if any light which would be passing from earth black hole and is within 1 cm form the center then it will not escape.  

3. How could scientist discovered it if we can’t see it?   

Light cannot escape form the black hole’s gravity. So, it is hard nut to crack to find the location of black hole. Due to its strong gravity, black hole creates a gravitational lens. Gravitational lens affects the travel path of the light emitted by other stars. We can locate the black hole by using this gravitational lens property.
 
Concept behind gravitational lens




Gravitational Lens

If suppose the black hole is located near any other star then it will start to pull the mass and other star particles towards it. Those particles and mass start to revolve around that black hole with very high speed forming a disc like structure called as ‘recreation disc’ (disc like Saturn have, only difference is revolving speed is considerably high in case of black hole).
 
Black hole pulling the mass from nearest star forming the Recreation disc

Those high speed revolving particles are electrically charged and their temperature becomes millions of Celsius. This is due to friction between them. Also, they are continuously get accelerated due to black hole. As a result, they start to emit the X-rays. If we find out these X-rays and its direction, then we can say that in that particular direction, black hole is present. We have Chandra X-ray telescope in space which is continuously tracking the X-ray signals coming from the universe.
 
Chandra X-ray Telescope

Well my friends, this is all about black hole and its facts, but there are so many mysterious things out there the universe is hiding. M87 black hole is just the beginning. Keep patience, good things take time.
 
Comment your opinion and your query. Thank you for your time.
Black Hole- A myth till now, A mystery yet to reveal. Black Hole- A myth till now, A mystery yet to reveal. Reviewed by Shubham on April 23, 2019 Rating: 5

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