Tinkle Explains
Tinkle Explains: Black Holes
Writer: Shreya Ghosh
Illustrator: Manas Bhagwat


One day, Mynah was on the way back from school with her friend Sheila. They were discussing black holes for their upcoming Space Week assignment. Let’s find out more! 

What are black holes?

When something goes beyond a certain region around the black hole, called the event horizon, the only way to escape is to be faster than light. However, nothing in the known universe is faster than light! Since even light cannot escape black holes, they are not visible. 

One way to understand the effect of black holes is through Albert Einstein’s general theory of relativity. Imagine space as made out of a taut fabric. This fabric’s components are space and time. If something heavy were placed on this taut fabric, it would curve the cloth around it. So, something that has strong gravity will bend space and time. Black holes, having very strong gravity, would cause a lot of such bending, causing light and other things in space to fall in if they get close enough.

How large are black holes?

There are also black holes that are medium in size, with a mass about 20 times that of the Sun. These are called stellar black holes. 

Black holes that have more mass than a million Suns are called supermassive black holes 

Black holes, as you may have understood from the atom-sized ones, are very dense; this means that they have a lot of matter condensed into a comparatively much smaller space!

How are black holes formed? 

Stars like our Sun have limited lives. Like humans and animals, they are born, have a life and then die. When they run out of the fuel that makes them burn, their cores become too heavy for them and they collapse inwards (implode). The outward parts of the stars, in turn, explode. This event is called a supernova. The collapsing core of the star eventually ends up as a point with no volume and infinite density. This means that this part virtually occupies no space but has a very high mass. This point is called the singularity of the black hole. 

Apart from a supernova, there are other ways in which black holes are formed as well. 

If they’re invisible, how are they observed? 

Due to their strong gravity, black holes have effects on the celestial objects around them, such as stars. Through these effects, we are able to detect their presence. The behaviour of these objects can be seen using special telescopes designed for the purpose. 

There is also an observatory called LIGO (Laser Interferometer Gravitational-Wave Observatory) that picks up on the gravitational waves that black holes create in space-time, and amplifies these enough so we can hear how they sound! Through calculations, the size and mass of the source is identified, and they are thus categorized as different objects, including black holes. 

A powerful radio telescope like the Event Horizon Telescope (EHT) can even photograph black holes, or more precisely, the gas that orbits them. In 2019, it released an image of M87*, the black hole at the centre of the Messier 87 galaxy. Its mass is 6.5 billion times that of the Sun! 

Recently, a black hole much nearer to us was also photographed by the EHT!

Wait! Why is there a black hole near us?

Theoretically, there is a black hole at the centre of every galaxy, that too a supermassive one. Even our galaxy, the Milky Way, has a supermassive black hole at the centre, called Sagittarius A* or Sgr A* for short. After a lot of difficulty in photographing it, the EHT succeeded in doing so.

What else is interesting about black holes?

  • The Sun is not large enough to turn into a black hole. 
  • Two black holes can merge and form a bigger black hole!  
  • Stephen Hawking posited that black holes do release particles, and this is called Hawking radiation. As they release this radiation, the black holes slowly disappear. However, for most of the known black holes, this will take even more time than the age of the universe! 
  • Black holes are also being studied as batteries due to their immense gravitational force, which could potentially be used to create gigantic electronic circuits and electric power! At the moment, this has not been practically carried out, but is an interesting line of research. 

Like Mynah and Sheila, we hope you enjoyed learning about this enigmatic part of space too!

Click here to learn about Supernova

Thumbnail Image Credits:


What Is a Black Hole? | NASA
Astrophysicist Explains Black Holes in 5 Levels of Difficulty | WIRED
black hole | Definition, Formation, Types, Pictures, & Facts | Britannica 
Einstein’s theory of general relativity | Space 
Einstein and General Relativity | NASA 
How Albert Einstein Developed the Theory of General Relativity | Britannica 
About | LIGO Lab | Caltech 
Astronomers Reveal First Image of the Black Hole at the Heart of Our Galaxy | Event Horizon Telescope 
NASA – Neutron Stars 
Milky Way Galaxy | Size, Definition, & Facts | Britannica 
Hawking radiation | astronomy | Britannica 
This Is What Happens When a Black Hole Eats a Black Hole | Smart News| Smithsonian Magazine 
10 Questions You Might Have About Black Holes – NASA Solar System Exploration 

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