Cuesta College, San Luis Obispo, CA
[20 points.] Red dwarfs in the disk of the Milky Way are never found near the spiral arm where they were born. Explain why this is so, using the properties of stars and galaxies.
Solution and grading rubric:
- p = 20/20:
Correct. Due to their extremely long lifetimes, red dwarfs will make many orbits around the Milky Way, long after being born in and drifting away from their molecular clouds of origin, in which star formation is triggered by passing through the density waves located at the spiral arms. - r = 16/20:
Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. At least understands lifetimes and Milky Way motions. - t = 12/20:
Contains right ideas, but discussion is unclear/incomplete or contains major errors. Understands only lifetimes, or Milky Way motions. - v = 8/20:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Explanation primarily based on moving away from molecular cloud due to drift, being pulled away by gravity from other stars and/or galaxies, dark matter/energy, "redshifts," or expansion of space. - 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 30676
p: 20 students
r: 6 students
t: 4 students
v: 16 students
x: 1 student
y: 1 student
z: 0 students
A sample "p" response (from student 0008):
Another sample "p" response (from student 2517), accompanied by a diagram:
Another sample "p" response (from student 9802):
A sample "r" response (from student 4080), with stars moving radially outwards from rather than tangentially around the center of the Milky Way:
A sample "v" response (from student 8675):
A sample "x" response (from student 1192), at least speculating that some sort of migration is involved:
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