What happens when a star exhausts its core hydrogen supply?
A)Its core contracts,but its outer layers expand and the star becomes bigger and brighter.
B)It contracts,becoming smaller and dimmer.
C)It contracts,becoming hotter and brighter.
D)It expands,becoming bigger but dimmer.
E)Its core contracts,but its outer layers expand and the star becomes bigger but cooler and therefore remains at the same brightness.

Question

Quizplus · Accepted Answer

When a star exhausts its core hydrogen supply, its core contracts under gravity, but the increased pressure and temperature ignite hydrogen in a shell surrounding the core. This causes the outer layers to expand, and the star becomes a red giant, which is bigger and brighter than it was in the main sequence phase.

What Happens When a Star Exhausts Its Core Hydrogen Supply