Astronomy quiz question: old star cluster with red dwarfs

Astronomy 210 Quiz 6, spring semester 2016
Cuesta College, San Luis Obispo, CA

Red dwarfs and __________ will be found in an old star cluster.
(A) massive main-sequence stars.
(B) medium mass protostars.
(C) white dwarfs.
(D) supergiants.

Correct answer (highlight to unhide): (C)

All stars in a star cluster are born at the same time, but undergo stellar evolution at different rates depending on their masses. Red dwarfs are low mass stars in their main-sequence stage, and evolve slower than medium-mass stars, and much slower than massive stars. So this old star cluster will have massive stars that have already gone through their protostar, main-sequence, supergiant and type II supernova stages; and also have medium-mass stars that have already gone through through protostar, main-sequence, giant, planetary nebula, and white dwarf stages.

Section 30674
Exam code: quiz06ncM7
(A) : 3 students
(B) : 5 students
(C) : 10 students
(D) : 2 students

Success level: 53% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.20

Section 30676
Exam code: quiz06sRR0
(A) : 9 students
(B) : 9 student
(C) : 26 students
(D) : 4 students

Success level: 55% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.43