Beginners guide to Black Holes

What is a Black Hole? A hole with empty space? You must have heard about Black Holes as one of the most fascinating and fiercest things in the universe. If so, then you have heard the right thing.

A Black Hole is a place in space where gravity is so strong that nothing, I mean nothing, not even light can escape from it. What happens to the matter after it has fallen into a Black Hole? Nobody knows for real.

Finally, we have it, the first picture of the Black Hole captured by the Event Horizon Telescope by combining eight ground-based telescopes across the globe. The feat that was thought be almost impossible a few years ago and now we have it. The image is of the supermassive Black Hole in the centre of the Messier 87 galaxy.

Why are they called Black Holes?

Because light can’t escape after it has fallen into a Black Hole. This means no light is reflected back for us to actually see it. This is what makes them invisible.

How are they formed?

A false color image of Cassiopeia A (Cas A)

A Black Hole is formed when large stars, much larger than Sun dies and goes supernova to form into a Black Hole. It is interesting to note that not all stars go supernova and all supernovas don’t turn into a Black Hole.

Indian Astronomer Chandrashekar gave a limit above which a star won’t form into a Black Hole. It will go Supernova and either turn into a neutron star or a Black Hole.

How big are Black Holes?

 There are mainly four types of Black Holes.

  1. Micro Black Holes

Stephen Hawking predicted that Black Holes as small as one atom but weighing as much as a large mountain could also exist in the universe.

  1. Stellar-mass Black Holes

They are the most commonly found stars in the universe. They can be 4 to 50 times massive than the Sun. They are formed due to the collapse of a massive star.

  1. Intermediate Black Holes

Intermediate Black Holes are formed when cluster of stars collide. They can turn into supermassive Black Holes. They can be more than 1000 times massive than the Sun.

  1. Supermassive Black Holes

This are the largest type of Black Holes found in our universe. They can easily be 1 million times bigger than the Sun. They grow by gathering mass from dust and gases around them. The Black Hole at the centre of the Milky Way, Sagittarius A is 4 million times more massive than Sun. It is located 26,800 light years from Earth.

Could a Black Hole destroy Earth?

Everyone must have thought of this question at least once. Can a Black Hole destroy Earth? Well on its day Black Holes can destroy almost anything. But Black Holes doesn’t go around eating planets and stars. Earth will not be destroyed because there is no Black Hole close to the Earth.

Even if we replace the Sun with a Black Hole with the same mass, Earth will not fall into a Black Hole because the gravity of the Black Hole will be the same as the Sun. So, all the planets including Earth would still revolve around the Sun.


What if I fell into a Black Hole?

Who doesn’t want to fall into a Black Hole? No! just kidding.

Journey to the Black Hole is a one-way journey, if you fall into it then you are not coming back. In theory, if you fall into a Black Hole than its gravity would stretch you like spaghetti.

Gravity would act on your body from all the sides. If you fall with your feet first then the gravity pulling your feet will be stronger than the gravity pulling your head because your feet will be closer to the Black Hole.

 You will be stretched until you can’t be stretched any further. When your body exceeds the molecular segments, you will be snapped into many pieces, leaving behind an unrecognisable array of particles. Scary isn’t it?

Is time affected by Black Holes?

Yes, it is said that time slows as we go close to the Black Hole. So, if you were to throw an object towards the Black Hole then it will become slower as it gets closer and closer to the Black Hole. Not only Black Holes, in theory, every big object affects time.

Every heavy object creates a bent in the spacetime curvature like the Sun. So, time will be slower near the Sun, because light travels faster in a straight line than a curved path. Black Holes are the most extreme example of how spacetime curvature is bent, so time will be slower near the Black Hole.

Some Facts about the Black Hole

1. Black Holes do not suck

What? Well, Black Holes are not vacuumed cleaners to suck matter into them, they are just any other object in space with high gravity. Black Holes do not suck matter instead matter falls into them

2. Black Holes evaporate with time


Stephen Hawking said that Black Holes loses its mass over time in the form of radiation called Hawking’s Radiation.

3. There is a supermassive Black Hole at the centre of our galaxy

Sagittarius A is thought to be 26000 light years from Earth.

4. Cygnus X-1 is the first object to be considered as a Black Hole

Cygnus  X-1 is located about 7,000 light-years from Earth in the constellation Cygnus. It was discovered in 1964 during a rocket flight and is one of the strongest X-ray sources seen from Earth. Cygnus X-1 has a mass 14.8 times that of the Sun.

5.White Holes

A White Hole is the opposite of Black Hole in a mathematical sense. White Hole also has an event horizon. Nothing outside a White Hole can enter and everything inside must be ejected out.

6. Black Holes are used in science fiction all the time

There are so many movies using Black Holes Interstellar, event horizon, star trek etc. Well, it’s impossible to list them all.

7. Einstein didn’t discover the Black Hole

He did not discover the existence of black holes, although his theory of relativity did predict their formation. Karl Schwarzschild gave a term called Schwarzschild radius, a measurement of how small you have to compress an object to create a black hole.

Long before this British scientist John Mitchell predicted the existence of dark stars, so massive that and so strong that not even light can escape.

8. Anything can become a Black Hole, in theory

If you can compress any object beyond a limit (Schwarzschild radius), then any object can become a black hole theoretically! The density increases so much that the gravitational pull causes the object to collapse in such a manner that even light can’t escape.

 If you shrunk our Sun down to a size of only 3.7 miles (6 km) across, for example, then you would have compressed all of the mass in our sun down to an incredibly small space, making it extremely dense and also making a black hole. Similarly, if you could shrink Earth to the size of a peanut then Earth can also turn into a Black Hole.

9. Black Holes can create a new universe

If you have heard of the Big Bang theory then the singularity which gave rise to the universe matches with the black hole’s singularity.

Singularity is a point where time stops and the time might start at the other end after the big bang.

10. Black Holes are pretty loud

Whenever something falls into the event horizon its accretion disks charges up and speeds very fast, close to the speed of light producing a pretty loud and weird sound.

Of course, you can’t hear the sound in the vacuum but with the help of special instruments, you can hear a bird chirping like sound.

4 thoughts on “Beginners guide to Black Holes”

    1. Hello! thank you… I am glad it helped you.
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