Astronomy quiz question: globular cluster locations

Astronomy 10 Quiz 11, Spring Semester 2008
Cuesta College, San Luis Obispo, CA

Astronomy 10 learning goal Q11.2

[3.0 points.] Which one of the following statements best describes what can be deduced from observing the positions of globular clusters in the halo of the Milky Way?
(A) The location of the center of the Milky Way.
(B) Globular clusters are composed of dark matter.
(C) The universe is steadily expanding.
(D) The spiral arm structure of the Milky Way.
(E) The location of metal-rich stars in the Milky Way.

Correct answer: (A)

Due to the dust and gas in the disk of the Milky Way, only a very small fraction of our galaxy is visible from the Earth. Thus to determine the overall size of the Milky Way, and the distance from the Earth to its center, it is necessary to observe the positions of globular clusters in the halo, which are visible well above and below the plane of the disk. Students who chose response (D) are probably confusing globular clusters with spiral arm tracers.

Student responses
Section 4160
(A) : 11 students
(B) : 1 student
(C) : 0 students
(D) : 22 students
(E) : 0 students