Astronomy midterm question: showerhead effect

Astronomy 10 Midterm 2, Spring Semester 2008
Cuesta College, San Luis Obispo, CA

Astronomy 10 learning goal M2.1

[15 points.] Explain why the meteors in a given shower would appear to be diverging from a fixed point in the sky, as seen from San Luis Obispo, CA.

Solution and grading rubric:

• p = 15/15:
  Correct. Describes and explains the "showerhead effect," where the parallel paths of comet debris particles appear to diverge away from a fixed point in the sky as the Earth passes through the debris.
  
• r = 12/15:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Typically describes, but does not fully explain the showerhead effect.
  
• t = 9/15:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Solidification age is reset, but due to loss/gain/renewal of unstable isotopes.
  
• v = 6/15:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. May discuss cause of meteor showers (when the Earth passes through the dust trail left by a comet), but not
  why they would appear to diverge from a fixed point in the sky.
  
• x = 3/15:
  Implementation/application of ideas, but credit given for effort rather than merit.
  
• y = 1.5/15:
  Irrelevant discussion/effectively blank.
  
• z = 0/15:
  Blank.
  

Grading distributions:
Section 4160
p: 21 students
r: 6 students
t: 4 students
v: 6 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 6421) appealing to "The Showerhead Effect":

A sample "p" response (from student 7045) appealing instead to "The Railroad Track Effect":
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