Question

What happens to the star's outer layers as the fuel in its core is used up?

They shrink and cool.
They shrink and heat up.
They expand and cool.
They expand and heat up.
Nothing. Only the interior changes.

Answer 1

When the fuel in the core of a star is used up, the star's outer layers expand and cool.

Step-by-step explanation:

When the fuel in the core of a star is used up, the star's outer layers begin to expand and cool.

As the core collapses under its own weight, heat is released and flows into a shell of helium just above the core. This helium is heated enough to start fusion and generate a new flow of energy.

The release of energy causes the outer layers of the star to expand, making the star grow until it reaches enormous proportions.