what is a black hole?

1a dying star

Imagine a star far bigger than our sun, burning fuel for millions of years, until one day it runs out.

2gravity wins

When the fuel dies, gravity wins. Nothing pushes back anymore, so the whole star collapses inward on itself.

3the singularity

It crushes down to a single point, packed so dense that its gravity becomes almost infinitely strong — a black hole is born.

4no escape

That circle is the event horizon — the point of no return. Cross it, and not even light moves fast enough to escape.

5accretion disk

Nearby gas and dust swirl in, heating up into a glowing disk before they vanish forever past the horizon.

6how we find them

We can't see a black hole directly, but we see its pull bending starlight and its disk glowing — that's how we found them.