20161008

Astronomy midterm question: Jupiter rising a few hours after sunrise?

Astronomy 210 Midterm 1, fall semester 2016
Cuesta College, San Luis Obispo, CA

The following claim was made on an online discussion board[*]:
Cte: If Jupiter can be seen in the west at sunset, then Jupiter is going to be rising a few 
 hours after sunrise.
Discuss why this answer is correct for an observer in San Luis Obispo, CA, and how you know this. Support your answer using a diagram showing the positions of the sun, Jupiter, and an observer on Earth. (Assume you can see planets in daylight.)

[*] answers.yahoo.com/question/index?qid=20120314164501AA0wF99.

Solution and grading rubric:
  • p:
    Correct. Complete diagram and reasoning includes the following explanations:
    1. for an observer on Earth at sunset (6 PM), Jupiter is placed in an orbit around the sun outside of Earth' orbit such that it is visible low over the west horizon;
    2. this observer at sunrise (6 AM) would not be able to see Jupiter (which does not appreciably move in its orbit during this time), as it would be below the horizon, such that waiting a few hours after sunrise is necessary for Jupiter to rise above the east horizon.
  • r:
    Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors.
  • t:
    Contains right ideas, but discussion is unclear/incomplete or contains major errors. Problems with either diagram or discussion. May have:
    1. Jupiter placed in a geocentric orbit around Earth, but in a manner consistent with being low in the west at sunset, and would rise shortly after sunrise; or
    2. Jupiter placed in an outer orbit around the sun such that it is seen in the east at sunset, and/or is already above the horizon at sunrise.
  • v:
    Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Diagram and discussion problematic.
  • x:
    Implementation/application of ideas, but credit given for effort rather than merit.
  • y:
    Irrelevant discussion/effectively blank.
  • z:
    Blank.
Grading distribution:
Section 70158
Exam code: midterm01s4uL
p: 12 students
r: 6 students
t: 20 students
v: 3 students
x: 1 student
y: 1 student
z: 0 students

A sample "p" response (from student 4050):

Another sample "p" response (from student 2600):

Yet another sample "p" response (from student 4581), instead using the fact that over the course of a day, Jupiter's position in the sky is fixed with respect to the sun in a graphical representation of the sun's and Jupiter's motion across the sky:

No comments: