Hello to everyone, ‘Into the unknown:The Black Hole’ ; isn’t it a mysterious and catchy title? of course it is and it should be, because black hole is supposed to be one of the greatest mystery in the scientific world & that’s why it feels catchy for every astronomy and physics lover.
What is it actually? What’s inside it ? Why it is named as a black hole? and what will happen if we go inside one?
There were many questions, actually still there are many but the curiosity played the important role here to found the answers. Many finest minds have contributed to unravel these mysteries such as Karl Schwarzschild, c.v.vishveshwara, S.Chandrashekhar, Stephen Hawking and many more.
WHAT IS IT ACTUALLY?
‘Black Hole‘; the name itself suggests that it is nothing but a hole which is totally black. Actually, Black hole is a cosmic body which has so strong gravitational force to attract everything around it and nothing can escape from it not even light!(horrible, isn’t it?), death of a star gives rise to a black hole.
So let’s talk about how stars are formed? Recipe of a star requires nothing but some nuclear fusion, some dust, some gas molecules from space. When hydrogen atoms comes in contact with each other forming a bond which gives rise to helium & as the number of helium atoms come together and very high temperature and pressure causes nuclear fusion leads to formation of a core of a star, a core of a star is nothing but the engine which drives the star and the helium can be supposed as a fuel of it which keeps star burning!!
This high energy formed inside a star keeps pushing the outer layers of a star and the star’s gravity pulls it inwards ( it’s a fight!); but as both forces are equal and opposite so star remains stable. But as the star grows older, the fuel inside it starts to exhaust and couldn’t keep up. This is a situation where a star is in its final stage which is known as ‘Red Giant’. When star dies i.e. a supernova ( A big explosion!) then the gravitational pull dominates over the inside energy of star resulting star starts to fall in its own centre which is known as ‘Gravitational collapse‘. this collapse compacts the mass of a big star into a tiny ball in space causes the infinite density and concentrated mass with intensified gravitational force object which is nothing but a ‘Black Hole’. Even light can not escape from it! ( Total horror!!)
WHY IT IS BLACK?
Why is it black then? because even light can not escape, OK but what of it? actually we can see an object and can sense its colors because a light ray falls on it and reflect back to our retina but as the escape velocity of a black hole is more than velocity of light that’s why light can not reflect and we can’t see it or see it black! one question, why do a light ray travelling with a straight path bends towards it?
Well, A legendary man named ‘Albert Einstein’ explained this phenomena; he derived the general theory of relativity which tells us that Space-Time is a fabric. Like stretched rubber sheet, inside it if a ball of a certain mass is placed then it creates a curvature, something like this happens in a space where a black hole with a massive mass compacted in it creates an infinite curvature and everything travelling near there like light gets attracted towards it!
HOW DO WE FIND THEM?
OK, but how does scientist know that they are there? Nice question! well, it could be figured out by observing the behaviour of stars around it ( they dance like a mad person with an invisible partner!). Black holes absorbs the energy of the nearest star and which can be observed well; it is like seeing harry potter movie! also they emits X-Rays and Gamma Rays bursts so it can be captured using instruments and detectors like Chandra X-Ray observatory by NASA.
Not every star comes out with a black hole usually. An Indian scientist S. Chandrashekhar stated that only a star having 3 times more mass than our sun’s mass can become a black hole after its death and this value is known as the ‘Chandrashekhar Limit’. Every other star which couldn’t satisfy above value forms into another like ‘white dwarfs’, ‘stellar’, ‘pulsars’, ‘ neutron stars’ these all are vast subjects themselves to study.
While collapsing into a black hole after a certain point collision stops and this is known as ‘freezing of the collision’ and that point is known as ‘Event Horizon’. It is nothing but a border which distinguishes a black hole and outside space. If someone crosses the event horizon then he/she can’t get out and every event happening inside it couldn’t be seen from outside; it is the end of the events. Another interesting thing is Time has no existence inside a black hole that makes it even more mysterious than before. our galaxy contains a supermassive black hole at its centre named ‘Sagittarius A‘ but don’t worry its far from our place.
There are many theories about black hole that it could be the way to another dimension; or it could contain another universe there are many; but there is one fact once you get inside one, no one can help you to get out from it! so try not to fall into one and be curious!
For more details about Black hole check our previous post.