## 20120501

### Astronomy midterm question: star cluster with type II supernovae?

Astronomy 210 Midterm 2, spring semester 2012
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?
ronwizfr: [A] very young cluster [instead of a very old cluster]...
Decide whether or not if this answer is correct, and how you know this. Explain using the properties and evolution of stars.

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:
Blank.
Section 30674
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):