The main sequence has a limit at the lower end because
A) low mass stars form from the interstellar medium very rarely.
B) low mass objects are composed primarily of solids, not gases.
C) pressure does not depend on temperature in degenerate matter.
D) the lower limit represents when the radius of the star would be zero.
E) there is a minimum temperature for hydrogen nuclear fusion (the definition of a star).

Question

Quizplus · Accepted Answer

The main sequence represents stars in which hydrogen fusion is occurring in the core. However, there is a minimum temperature at which hydrogen fusion can occur, and stars with temperatures below this limit cannot sustain fusion reactions in their cores. Therefore, the main sequence has a lower limit where stars cannot exist due to the lack of nuclear fusion. The main sequence represents stars that are fusing hydrogen in their cores. There is a minimum temperature required for hydrogen fusion to occur, which sets the lower limit of the main sequence. Therefore, choice E is the correct answer. The other options do not provide an accurate explanation for why there is a limit at the lower end of the main sequence.

The Main Sequence Has a Limit at the Lower End