The main reason that stars evolved off the main sequence is because they are becoming less massive as energy is lost into space from the proton- proton cycle.

Question

Quizplus · Accepted Answer

Stars evolve off the main sequence primarily because they exhaust their core hydrogen fuel, leading to changes in their internal structure and energy production mechanisms, not because they are becoming significantly less massive through energy loss.

The Main Reason That Stars Evolved Off the Main Sequence