How do large-mass stars in the upper region of the main sequence produce energy?
A) by fusing hydrogen using the proton-proton chain
B) by fusing hydrogen using the CNO cycle (carbon-nitrogen-oxygen)
C) by fusing hydrogen using both the CNO ccle and the proton-proton chain
D) by fusing hydrogen using the HNO ccle (hydrogen-nitrogen-oxygen)
E) by fusing helium using the HeNO ccle (helium-nitrogen-oxygen)

Question

Quizplus · Accepted Answer

Large-mass stars in the upper region of the main sequence produce energy by fusing hydrogen using the CNO cycle (carbon-nitrogen-oxygen). This is because the CNO cycle is more efficient at high temperatures and densities than the proton-proton chain, which is used by smaller stars in the lower region of the main sequence.

How Do Large-Mass Stars in the Upper Region of the Main