Astronomy midterm question: Jupiter, not Venus low in the west at dawn

Astronomy 210 Midterm 1, spring semester 2019
Cuesta College, San Luis Obispo, CA

An astronomy question on an online discussion board was asked and answered[*]:

deanmajiet65: Just before dawn, I saw a planet in the sky in the west. Is it Jupiter or Venus?
Rich: It's not Venus. You were facing west, so that was Jupiter.

Discuss why this planet could not be Venus, and would have to be Jupiter 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, Venus, Jupiter, Earth, and an observer on Earth.

[*] answers.yahoo.com/question/index?qid=20090727104303AA5cFyR.

Solution and grading rubric:

• p:
  Complete diagram and reasoning includes the following explanations for how it is possible for an observer on Earth to be able to see Jupiter, but not Venus in the west at dawn:
  1. places observer on Earth at dawn (or some time after midnight but before sunrise), with east and west horizons clearly indicated; and
  2. is able to place Jupiter (in an outer orbit) such that it is visible above the west horizon for this observer, and also indicates how Venus (in an inner orbit) can only be seen in the east horizon if it is visible at all at dawn.
• r:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Typically diagram is correct, but supporting argument is contradictory or incomplete.
• t:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. May have an observer at sunset instead of sunrise, and/or switched east/west horizons; but still has Jupiter and Venus along outer and inner orbits around the sun, respectively.
• v:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Some attempt at diagram(s), but no clear indication of observer/horizon on Earth and how placement of outer and inner planets would (or would not) be visible at dawn in the west. Typically misplaces Jupiter and Venus in their relative outer/inner orbits around the sun.
• x:
  Implementation/application of ideas, but credit given for effort rather than merit.
• y:
  Irrelevant discussion/effectively blank.
• z:
  Blank.

Grading distribution:
Section 30674
Exam code: midterm01NtwT
p: 17 students
r: 3 students
t: 10 students
v: 4 students
x: 0 students
y: 1 student
z: 0 students

Section 30676
Exam code: midterm01SFBk
p: 26 students
r: 2 students
t: 9 students
v: 3 students
x: 2 students
y: 1 student
z: 1 student

A sample "p" response (from student 7563):
A sample "v" response (from student 1735), with both Venus and Jupiter as inner planets, and with east and west horizons switched for an observer on Earth, just before dawn: