Question

In a star's evolutionary life, the asymptotic giant branch (AGB) is the

A) helium core fusion phase.
B) pre-main-sequence core hydrogen fusion phase.
C) hydrogen shell fusion phase prior to helium ignition in the core.
D) helium shell fusion phase.

Answer 1

The asymptotic giant branch (AGB) is the phase in a star's evolutionary life where the star becomes a red giant again after the helium flash. During this phase, the core contracts while the outer layers expand due to hydrogen fusion in a shell outside the core.

Step-by-step explanation:

The asymptotic giant branch (AGB) is the phase in a star's evolutionary life where the star becomes a red giant again after the helium flash. During the AGB phase, the star's core contracts while the outer layers expand due to hydrogen fusion in a shell outside the core. As a result, the star gets larger, redder, and more luminous as it expands and cools.