In the first stage after main-sequence hydrogen fusion, the envelope of the star is pushed outward to expand. The nuclear reactions that produce the outward pressure for this expansion are

Question

Quizplus · Accepted Answer

In the first stage after main-sequence hydrogen fusion, the core contracts and heats up, causing hydrogen fusion to occur in a shell surrounding the inert helium core. This shell hydrogen fusion provides the energy to push the envelope of the star outward, leading to its expansion.

In the First Stage After Main-Sequence Hydrogen Fusion, the Envelope