Astronomy quiz question: same-size giant and supergiant

Astronomy 210 Quiz 4, Spring Semester 2011
Cuesta College, San Luis Obispo, CA

A supergiant has the same size as a giant. As the supergiant is more luminous, it will have a __________ than the giant.
(A) cooler temperature.
(B) hotter temperature.
(C) larger parallax angle.
(D) smaller parallax angle.

Correct answer: (B)

The Stefan-Boltzmann law states that luminosity is proportional to size (that is, surface area) and temperature (T^4). Since these two stars have the same size, then the more luminous star must be hotter than the less luminous star.

Section 30676
(A) : 2 students
(B) : 33 students
(C) : 3 students
(D) : 0 students

"Success level": 81% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.27
Exam code: quiz04s0sO