What happens when a star runs out of fuel?

A star is like a giant, super-hot birthday cake that’s been burning for millions of years, and when it runs out of fuel, it has one big party.

A star shines because it's having a chemical reaction inside, kind of like mixing baking powder into a cake. The fuel is hydrogen, which turns into helium through this process. It’s like your favorite snack, you can only eat so much before you’re full.

When the star uses up all its hydrogen, it stops being able to keep itself hot and bright. It starts to cool down, and its outer layer puffs up, making it look like a balloon that’s been filled with air. This is called a red giant, it's still glowing, but now it looks softer and bigger.

Eventually, the star lets go of all the stuff it doesn’t need anymore, and what’s left becomes a white dwarf, like a tiny, glowing ember from a fire that’s almost gone.