Black Holes
What is a black hole?
What actually is a black hole? So, a black hole is actually a gravitational field. A really strong one in that case. It can even suck in any light. That's how strong it is.
So, you all know that in order for us to see something, we need light. But since even light can't escape a black hole, we're practically unable to see a black hole with our naked eye.
A black hole appears when a huge amount of matter is compressed into a very low amount of volume. Think of it like this. Imagine a star with a hundred times of mass as our own sun. That star has a much stronger gravitational field. Now compress that same star into the size of New York city. What would happen? The intensity of that gravitational field will be so high. It will be so high that even light can't escape it. That's simply what a black hole is.
How is a black hole born?
The birth of a black hole is the death of a star. Now what the hell was that? A star consists of a bunch of gasses. These gases react in a way called nuclear fusion. I'm not going to go into detail on nuclear fusion right now. What you need to know is this nuclear fusion creates an inward pressure inside the star causing it to expand. This is called radiation pressure. Easy enough to understand right? Then why doesn't a star keep expanding? Why is it just a huge fireball? The reason is gravity. The mass of these said gasses create a gravitational force causing the star to collapse. The equilibrium of this gravitational force and radiation pressure is what keeps the star intact. These gasses are like fuel. They'll run out eventually. This will cause the equilibrium to break and the star will collapse on itself because of the gravity. Thus, the star will turn into either a neutron star or a black hole depending on the mass of the star. If the star doesn't have enough mass to turn into a black hole, it'll turn into a neutron star or a white dwarf.
History
In 1916, the general relativity of Albert Einstein implies a possibility for the black holes to exist. The term "black hole" was first used in 1971 when the American physicist John Wheeler discovered a physical black hole. And in 2019, the most recent development was photographing an actual black hole. A lot of you might have seen this by now.
When we hear the word black holes, the first thing that comes to our mind is something very large. But scientists say that there are atomic size black holes as well. Even though these are small black holes the mass of these are equivalent to very large mountains.
Black holes can be divided into 3 main categories such as stellar black holes, supermassive black holes, and intermediate black holes. Let's look into these now.
Stellar black holes
The mass of a stellar black hole can be about 20 times the mass of our sun. When the star is dying it can collapse into itself to create either a neutron star, white dwarf, or a stellar black hole. If the mass of the star is equal to or less than the sun, it's likely to form a white dwarf. If it's typically more than 8 solar masses, it'll turn into a neutron star. If it's more than 20 solar masses it'll turn into a stellar black hole.
Supermassive black holes
The largest of the black holes are called suppermassive black holes. The mass of these can be more than a million solar masses. In the middle of almost every galaxy, there is a supermassive black hole. The supermassive black hole in the middle of our milky way is called "Sagittarius A*". This has a mass of around 4 million solar masses.
Intermediate black holes
Recent research depicts that there is another category of black holes in between stellar and supermassive. These are intermediate black holes. These are believed to exist in the middle of dwarf galaxies. Clear evidence for the existence of these is still missing. However, there are subtle hints.
Content of a black hole
There are three main parts of black hole. Those are singularity, inner event horizon, and outer event horizon.
The event horizon is like the boundary line of the black hole. Inside this event horizon, the escape velocity is greater than the speed of light. Hence, even light can't escape inside this event horizon. The radius of this event horizon is called the Schwarzchild radius. It is named in honour of the German physicist Karl Schwarzchild.
Singularity is where all the mass is centered. It has a very low volume and a very high mass.
So, that's it for today folks. If you have any doubt that we'll ever be engulfed by a black hole, no need to be scared. There's not a single black hole nearby enough to do such a thing and our sun doesn't have enough mass to turn into a black hole. So, I'm ending this article in hope of meeting you all in another day.
Article by - Anupama Dewpura