Astronomy 210 Quiz 6, Spring Semester 2009
Cuesta College, San Luis Obispo, CA
The ages of globular cluster stars in the Milky Way halo are determined from:
(A) parallax.
(B) the turn-off point on an H-R diagram.
(C) width of their absorption spectra lines.
(D) their colors.
Section 30676
(A) : 8 students
(B) : 13 students
(C) : 19 students
(D) : 14 students
Correct answer: (B)
The most massive stars left on the main sequence line on an H-R diagram gives the age of the star cluster, because all the stars started their formation at the same time, and the more massive stars have shorter lifetimes (and leave the main sequence line faster) than the less massive stars. Response (A) would determine the distance to stars; response (C) would give an indication of their densities/luminosity class; response (D) would be correlated with the surface temperatures of these stars.
"Difficulty level": 31% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.06
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