Astronomy quiz question: extremely young star cluster stars

Astronomy 210 Quiz 5, spring semester 2013
Cuesta College, San Luis Obispo, CA

__________ will be found in an extremely young star cluster.
(A) Giants.
(B) Red dwarfs.
(C) Supergiants.
(D) White dwarfs.

Correct answer: (C)

Massive stars (which become supergiants) evolve faster than medium-mass stars (which become giants, then white dwarfs), which evolve faster than low-mass stars (red dwarfs). Since in a star cluster all stars are born at the same time, massive stars will become supergiants before the medium-mass main-sequence stars become giants and subsequently white dwarfs, and the low-mass stars reach the main-sequence to become red dwarfs.

Section 30674
Exam code: quiz05n3wT
(A) : 5 students
(B) : 8 students
(C) : 8 students
(D) : 4 students

Success level: 36% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.86

Section 30676
Exam code: quiz05s0uL
(A) : 4 students
(B) : 14 students
(C) : 12 students
(D) : 7 students

Success level: 37% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.36