Gravity pulls in. Core heat pushes out.
Its fuel runs out. The push stops.
In a far heavier star, gravity wins.
The core collapses. The outer layers blow away.
Why can't anything get out? Take the Sun.
To leave its surface takes about 618 km/s.
Squeeze it smaller: the pull at its surface grows.
Escaping takes more and more speed.
Its light turns red and dim.
About 6 km across: not even light gets out.
Light that passes close is bent.
Closer still, it falls in.
Some swings all the way around.
The Sun is too light to collapse like this.
A black hole is not a hole. It is mass squeezed small.