Astronomy quiz question: star cluster with white dwarfs

Astronomy 210 Quiz 5, fall semester 2011
Cuesta College, San Luis Obispo, CA

A star cluster containing white dwarfs would also have:
(A) medium-mass main sequence stars.
(B) massive protostars.
(C) red dwarfs.
(D) supergiants.

Correct answer: (C).

White dwarfs are the end-stage of medium-mass stars, so medium-mass main sequence stars cannot be in the same star cluster as white dwarfs. Supergiants are the end-stages of the massive stars; while massive protostars are the start of massive stars, and as they evolve much more quickly than medium-mass stars, they cannot be in the same star cluster as white dwarfs. Red dwarfs are the main sequence stage of low-mass stars, and as they evolved much slower from protostar to main sequence stars, they are the most plausible of the given choices to be found in the same star cluster as white dwarfs.

Section 70158
Exam code: quiz05SpRn
(A) : 15 students
(B) : 5 students
(C) : 6 students
(D) : 6 students
(No response: 1 student)

Success level: 25% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.33

Section 70160
Exam code: quiz05nUc7
(A) : 9 students
(B) : 3 students
(C) : 11 students
(D) : 4 students

Success level: 45% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.46