Astronomy quiz question: massive vs. medium-mass main-sequence luminosity

Astronomy 210 Quiz 5, Fall Semester 2009
Cuesta College, San Luis Obispo, CA

Massive main-sequence stars are more luminous than low-mass main-sequence stars because massive main-sequence stars have:
(A) greater core pressures and temperatures.
(B) wider absorption lines.
(C) greater amounts of unstable heavy elements.
(D) more convection.

Correct answer: (A)

High pressures and temperatures are required to initiate fusion (whether proton-proton or CNO cycle), in order to overcome the repulsive forces between positively charged nuclei. Greater pressures and temperatures in cores of massive main-sequence stars will result in faster fusion rates, and thus brighter luminosity than medium-mass main-sequence stars.

Section 70160
(A) : 33 students
(B) : 2 students
(C) : 1 students
(D) : 2 students

Success level: 86% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.09