Astronomy in-class activity: monolithic collapse hypothesis, stellar populations

Astronomy 210 In-class activity 22 v.16.05.04, spring semester 2016
Cuesta College, San Luis Obispo, CA

Students find their assigned groups of three to four students, and work cooperatively on an in-class activity worksheet to discuss different metallicities and ages of stars in the monolithic collapse hypothesis of the Milky Way.

Astronomy quiz question: globular cluster star formation

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

Astronomy 10 learning goal Q11.5

[3.0 points.] Which one of the following statements best explains why there are no young stars in the halo clusters of the Milky Way?
(A) There are no longer enough heavy elements remaining in the halo.
(B) There are not enough gravitational forces in the halo for new stars to form.
(C) The dark matter in the halo prevents new stars from forming there.
(D) All of the metal-rich stars in the halo clusters have already become metal-poor stars.
(E) All of the interstellar hydrogen in the halo moved into the disk.

Correct answer: (E)

According to the monolithic formation theory of the Milky Way, the gas and dust in our galaxy was originally spherically shaped. Then as the first-generation stars of the globular clusters formed, hydrogen in the Milky Way gradually collapsed into the thin disk structure that it has today. Thus no new stars can form in the relatively empty spherical halo that surrounds the flattened Milky Way.

Student responses
Section 5166
(A) : 3 students
(B) : 16 students
(C) : 6 students
(D) : 7 students
(E) : 18 students

Astronomy quiz question: globular cluster age

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

Astronomy 10 learning goal Q11.5

[3.0 points.] Which one of the following statements best supports the theory that globular cluster stars in the halo of the Milky Way must be older than stars in the disk?
(A) Globular cluster stars are more abundant.
(B) Globular cluster stars are more luminous.
(C) Globular cluster stars are metal-rich.
(D) Globular clusters do not contain massive main sequence stars.
(E) Globular clusters do not contain dark matter.

Correct answer: (D)

Massive stars have much shorter main sequence lives than medium mass and low mass stars, thus globular clusters, being older, do not have massive main sequence stars. Note that responses (B) and (C) would correspond to very young stars.

Student responses
Section 4160
(A) : 1 student
(B) : 3 students
(C) : 12 students
(D) : 16 students
(E) : 1 student

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