Astronomy quiz question: spiral arm tracers

Astronomy 210 Quiz 6, fall semester 2011
Cuesta College, San Luis Obispo, CA

Spiral arms can be traced through the sun's neighborhood by locating the positions of spiral tracers such as:
(A) Cepheid variable stars.
(B) globular clusters.
(C) type Ia and type II supernovae.
(D) massive stars.

Correct answer: (D).

Massive stars are luminous and short-lived, so they only be located near where they were born from a spiral arm density wave. Cepheid variable stars are used to determine the distances to globular clusters in the halo of the Milky Way, and the distribution of globular clusters is used to locate the center of the Milky Way. Observations of type Ia and type II are used to determine the distances to other galaxies.

Section 70158
Exam code: quiz06pOp1
(A) : 9 students
(B) : 11 students
(C) : 4 students
(D) : 7 students
(No response: 1 student)

Success level: 27% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): -0.13

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