During which of the following phases of life is a star's pressure and gravity out of equilibrium?
A) Main sequence
B) Helium core fusion
C) A star is never out of equilibrium.
D) Red giant
E) White dwarf

Question

Quizplus · Accepted Answer

During the red giant phase, a star's pressure and gravity are out of equilibrium. This is because the stellar core has exhausted its supply of hydrogen fuel, causing the core to contract and increase in temperature. As a result, the outer layers of the star expand and cool, increasing their surface area and therefore decreasing their surface gravity. This creates a situation where the pressure in the outer layers is not able to counteract the force of gravity, causing the star to become unstable.

During Which of the Following Phases of Life Is a Star's