Astronomy

How Are Black Holes Formed in the Universe?

The life story that ends in a black hole

1. The star shines — a massive star burns fuel in its core, pushing outward against gravity pulling inward.
2. The fuel runs out — the outward push stops and gravity wins.
3. Collapse and explosion — the core falls inward while the outer layers blast away as a supernova.
4. A black hole is born — if the leftover core is heavy enough, it keeps shrinking until it becomes a black hole.

Important: not every star becomes a black hole. Our Sun is not massive enough, so it will end its life in a much gentler way.

What is the event horizon?

Every black hole is surrounded by an invisible boundary called the event horizon. Outside it, things can still fly away. Cross it and there is no coming back — not even light, the fastest thing in the universe.

That is also why a black hole looks black. Not because it is a hole, but because no light from inside ever reaches your eyes.

Types of black holes

If we cannot see one, how do we know they exist?

• Watch the surroundings — gas and dust falling in heat up and glow brightly before they vanish.
• Watch nearby stars — they orbit an empty-looking point, which means something very heavy sits there.
• Photograph its shadow — in 2019 scientists released the first image of the dark region around the black hole in galaxy M87.

Our own galaxy has a supermassive black hole at its centre. It is very far away and Earth is perfectly safe — black holes do not vacuum up the whole universe the way movies suggest.

astroQ Explorer Corner

Comet the Cat says

Many people picture a black hole as a giant vacuum cleaner swallowing everything. Not true! Swap the Sun for a black hole of the same mass and Earth would orbit exactly as before — just in the dark.

Byte the Robot says

Today's hard word: event horizon. Picture the line painted at your school gate — step past it and you are properly inside, with no stepping back out.