All stars turn hydrogen into helium...
- A cloud of gas becomes a star when nuclear reactions
(changing hydrogen into helium) start in the core of the star.
- A star's core has to be pretty hot in order to start these reaction,
but these reactions create even MORE heat.
- This energy heats up the gas, and the gas wants to expand.
But, gravity is pushing it back.
- A star's life is ruled by the battle between
gravity pushing in towards
the center of the star and gas pressure pushing out.
What happens when a star runs out of hydrogen?