Cuesta College, San Luis Obispo, CA
[20 points.] Shown at right is an H-R diagram of a star cluster, where all of these stars have the same age. Discuss whether this star cluster is very young or is very old, and explain why.
Solution and grading rubric:
- p = 20/20:
Correct. Massive stars evolve quickly, and have already gone through their main sequence lifetimes to the supergiant stage, so this cannot be a very young star cluster. Low mass stars evolve slowly, so for these stars to have reached the main sequence, this must be a very old star cluster. - r = 16/20:
Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. - t = 12/20:
Contains right ideas, but discussion is unclear/incomplete or contains major errors. May state that this is a young star cluster, but understands how massive and low mass stars evolve differently. - v = 8/20:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Uses other criteria to determine age of star cluster. - x = 4/20:
Implementation/application of ideas, but credit given for effort rather than merit. - y = 2/20:
Irrelevant discussion/effectively blank. - z = 0/20:
Blank.
Section 70160
p: 14 students
r: 1 student
t: 11 students
v: 3 students
x: 0 students
y: 0 students
z: 0 students
A sample "p" response, discussing the "house party" analogy of how stellar evolution rates depend on mass (from student 3089):
1 comment:
I bet you didn't think any students would respond did you?!
Well you were wrong, so wrong...
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