Cuesta College, San Luis Obispo, CA
An astronomy question on an online discussion board[*] was asked and answered:
Pd: Can there be old blue stars in an old star cluster?Discuss why this answer is correct, and how you know this. Explain using the properties of mass and stellar lifetimes, evolution of stars, and star cluster ages.
rcp: Not really...
Solution and grading rubric:
Correct. Understands that for stars in an old cluster the only blue stars must be massive main-sequence stars, and evolve very quickly, and will have already exploded as type II supernovae.
Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors.
Contains right ideas, but discussion is unclear/incomplete or contains major errors.
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Garbled discussion of properties and evolution of stars.
Implementation/application of ideas, but credit given for effort rather than merit. Discussion other than that of the properties and evolution of stars.
Irrelevant discussion/effectively blank.
Exam code: finalS1tH
p: 18 students
r: 5 students
t: 6 students
v: 5 students
x: 0 students
y: 0 students
z: 2 students
A sample "p" response (from student 1209):
Another sample "p" response (from student 2013):