Question

What phase of a low mass star's life has a core with active helium fusion and a shell of hydrogen fusion?

1) main sequence
2) red giant
3) horizontal branch
4) asymptotic giant branch

Answer 1

The phase of a low mass star's life with active helium fusion in the core and hydrogen fusion in a shell is the horizontal branch.

Step-by-step explanation:

The phase of a low mass star's life that has a core with active helium fusion and a shell of hydrogen fusion is known as the horizontal branch. During this stage, following the red giant phase, the star's core becomes hot enough to ignite helium into carbon in a process known as the triple-alpha process. The hydrogen fusion continues in a shell surrounding the core, and the star achieves a sort of balance, regaining a more stable structure after the tumultuous changes it goes through as it leaves the main sequence and passes through the red giant phase.