Question

The core of a red supergiant star stops shrinking because its ________.

1) temperature decreases
2) pressure decreases
3) gravity decreases
4) fusion reactions stop

Answer 1

The core of a red supergiant star stops shrinking because its fusion reactions stop when helium is exhausted and no further fusion processes that can generate sufficient pressure to counteract gravity become possible.

Step-by-step explanation:

The core of a red supergiant star stops shrinking because its fusion reactions stop. This occurs in the process of aging and dying of the star. Specifically, this cessation happens after the star has used up its helium for the triple-alpha process, where three helium atoms fuse to form a single carbon nucleus. Once energy generation from helium fusion ceases, there's no longer counter-pressure to the gravity trying to compress the core, leading to it shrinking and heating until no further fusion reactions take place. It's this lack of further fusion processes that ultimately halts the contraction of the core.