Astronomy quiz question: halo vs. disk population star age

Astronomy 210 Quiz 6, Fall Semester 2010
Cuesta College, San Luis Obispo, CA

Evidence that halo population stars are older than disk population stars is that halo population stars:
(A) contain dark matter.
(B) are less massive.
(C) have dimmer luminosities.
(D) have fewer absorption lines.

Correct answer: (D)

Each element will produce its own characteristic set of absorption lines. A star that had formed recently will be metal-rich, and have many absorption lines, while a star that had formed a long time ago will be metal-poor, and have fewer absorption lines.

Section 70158
(A) : 2 students
(B) : 8 students
(C) : 12 students
(D) : 22 students

"Success level": 53% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.34

Section 70160
(A) : 4 students
(B) : 4 students
(C) : 6 students
(D) : 23 students

"Success level": 66% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.71