Cuesta College, San Luis Obispo, CA
Discuss how it would be possible to observe a massive star during its main-sequence lifetime, while this star is actually a supergiant. Explain using the properties of mass and stellar lifetimes, and light.
Solution and grading rubric:
- p:
Correct. Explains how the finite speed of light causes distant objects to appear as they did in the past, such that a massive star will still appear to be in its main-sequence lifetime, despite having already become a supergiant. - r:
Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. At least recognizes that distant objects appear as they do in their past, or that the vast distances and/or finite speed of light is relevant. - t:
Contains right ideas, but discussion is unclear/incomplete or contains major errors. - v:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Discussion based on short lifetimes, bright luminosities, and/or fast fusion rates of massive stars. - x:
Implementation/application of ideas, but credit given for effort rather than merit. Implausible evidence/methods/discussion. - y:
Irrelevant discussion/effectively blank. - z:
Blank.
Section 70160
p: 22 students
r: 5 students
t: 0 students
v: 15 students
x: 0 students
y: 0 students
z: 0 students
A sample "p" response (from student 7272):
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