Astronomy quiz question: hottest star

Astronomy 210 Quiz 4, Spring Semester 2010
Cuesta College, San Luis Obispo, CA

Which star is hottest?
(A) A0 white dwarf.
(B) B0 main-sequence star.
(C) G5 giant.
(D) M5 main-sequence star (red dwarf).

Correct answer: (B)

Using the OBAFGKM spectral type mnemonic, or reading off of an H-R diagram (provided on this quiz), the B0 main-sequence star is the hottest, followed by the A0 white dwarf, G5 giant, and M5 red dwarf. Apparently a few students chose the A0 white dwarf for being "white-hot" (when in fact the B0 main-sequence star would be a hotter white-, or even blue-hot in appearance). Notably, this quiz was given the week after an OBAFGKM poetry slam.

Section 30674
(A) : 4 students
(B) : 39 students
(C) : 0 students
(D) : 0 students

"Success level": 91% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.25

Section 30676
(A) : 14 students
(B) : 42 students
(C) : 6 students
(D) : 3 students

"Success level": 67% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.30

Previous post: Astronomy quiz question: hottest star, (spring semester 2009).