Astronomy 210 Quiz 6, Fall Semester 2009
Cuesta College, San Luis Obispo, CA
Evidence that entire galaxies were captured and absorbed by the Milky Way is that:
(A) the sun has metal absorption lines.
(B) not all globular clusters have the same age.
(C) globular clusters have randomly tipped, elliptical orbits.
(D) the halo is composed of dark matter.
Correct answer: (B)
According to the monolithic collapse model, the Milky Way evolved from a spherical shape to its current disk shape, leaving behind the globular clusters out in its halo. Thus globular clusters should all have the identical (old) ages (as determined from the lack of metal absorption lines, and their H-R diagram turn-off points), while the disk should be comprised of mixed age (old and newer) stars. However, the presence of globular clusters of different ages indicates that they may have been inherited from smaller dwarf galaxies.
Section 70158
(A) : 2 students
(B) : 30 students
(C) : 7 students
(D) : 3 students
Success level: 74% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.49
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