Cuesta College, San Luis Obispo, CA
Astronomy 10 learning goal 11.5
[15 points.] Discuss the evidence that stars in the halo clusters of the Milky Way are older than stars in the disk of the Milky Way.
Solution and grading rubric:
- p = 15/15:
Correct. Halo cluster stars are known to be older because there are no massive stars left on the main sequence, and their spectra are metal-poor; in contrast to the stars in the disk of the Milky Way, of which there are many massive stars on the main sequence (thus formed relatively recently), and their spectra are metal-rich (heavy elements from past type II supernovae). - r = 12/15:
Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Cites plausible, but somewhat less convincing evidence (e.g., massive stars are only found in the disk of the Milky Way). - t = 9/15:
Contains right ideas, but discussion is unclear/incomplete or contains major errors. Uses argument that Milky Way evolved from spherical- to disk-shaped, when in fact this theory of evolution is based on the fact that halo cluster stars are older than disk stars (due to the reasons cited in (p)). - v = 6/15:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. - x = 3/15:
Implementation/application of ideas, but credit given for effort rather than merit. - y = 1.5/15:
Irrelevant discussion/effectively blank. - z = 0/15:
Blank.
Section 4160
p: 7 students
r: 6 students
t: 6 students
v: 13 students
x: 2 students
y: 1 student
z: 0 students
Section 5166
p: 4 students
r: 1 student
t: 10 students
v: 21 students
x: 0 students
y: 2 students
z: 0 students
A sample "p" response (from student 1721):
Student 1882 gets a "x" for circular reasoning:
Student 0000 gets a "y" for begging the question:
Student 1337 gets a "y" for a display of artistic skill:
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