Astronomy quiz question: end of main-sequence lifetime

Astronomy 210 Quiz 5, fall semester 2012
Cuesta College, San Luis Obispo, CA

A massive star will end its main-sequence lifetime when:
(A) gravity is too strong.
(B) convection currents stop.
(C) core temperatures get too cold.
(D) no hydrogen is left in the core.

Correct answer: (D)

The longest phase of a star's life is when it is on the main-sequence, which is when energy is released from hydrogen as it fuses into helium, and ends when all hydrogen available in the core is depleted.

Section 70158
Exam code: quiz05sNv4
(A) : 3 students
(B) : 1 student
(C) : 6 students
(D) : 23 students

Success level: 72% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.31

Section 70160
Exam code: quiz05N3w7
(A) : 1 student
(B) : 3 students
(C) : 0 students
(D) : 23 students

Success level: 86% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): -0.14