Cuesta College, San Luis Obispo, CA
[20 points.] An astronomy question on an online discussion board(*) was asked and answered:
Fey Lin: If you were looking for massive-star supernovae, in which type of star cluster would you look?Decide whether or not if this answer is correct, and how you know this. Explain using the properties and evolution of stars.
ronwizfr: [A] very young cluster [instead of a very old cluster]...
Solution and grading rubric:
- p = 20/20:
Correct. Understands that massive stars evolve faster than low-mass stars, such that a younger star cluster will have massive stars that will have already gone through their protostar to main sequence to supergiant phases, in order to soon explode as (type II) supernovae.
- 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. At least understands correlation between mass and main sequence lifetime.
- v = 8/20:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner.
- x = 4/20:
Implementation/application of ideas, but credit given for effort rather than merit. Discussion other than that of the properties and evolution of stars.
- y = 2/20:
Irrelevant discussion/effectively blank.
- z = 0/20:
Exam code: midterm02n4Rg
p: 20 students
r: 1 students
t: 3 students
v: 9 students
x: 0 students
y: 0 students
z: 0 students
A sample "p" response (from student 7538), showing the evolution of the star cluster on an H-R diagram:
Another sample "p" response (from student 5213), discussing the relative evolution rates of massive vs. medium mass stars:
Yet another sample "p" response (from student 2393), using the "House Party" analogy of stellar evolution rates:
A sample "v" response (from student 1313):