Astronomy midterm question: Jupiter spotted as military drone?

Astronomy 210 Midterm 1, fall semester 2013
Cuesta College, San Luis Obispo, CA

Astronomers from the Indian Institute of Astrophysics were asked whether an object in the sky was a Chinese military drone.[*]

[The object] appeared [just above] the horizon at about [sunset] and remained visible until [just before sunrise]. The astronomers have concluded that the object...is Jupiter.

Discuss how this planet provides a plausible explanation for this sighting. Support your answer using a diagram showing the positions of the sun, Jupiter, Earth, and an observer on Earth.

[*] Adapted from G.S. Mudur, "By Jupiter! China Spy in Sky—Intruders over Ladakh Turn Out to be Two Planets," The Telegraph, July 24, 2013, http://www.telegraphindia.com/1130724/jsp/frontpage/story_17150854.jsp.

Solution and grading rubric:

• p = 20/20:
  Correct and complete diagram, with the sun, Jupiter (just past opposition), and an observer on Earth); shows and discusses how Jupiter would be just above the east horizon at sunset, and remain visible until setting on the west horizon before dawn.
• r = 16/20:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Diagram and/or explanation has minor errors.
• t = 12/20: Contains right ideas, but discussion is unclear/incomplete or contains major errors. Problems with either diagram or discussion. At least understands that Venus must be just above the sun when the sun is at (or just below) the horizon.
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Diagram and discussion problematic.
• x = 4/20:
  Implementation/application of ideas, but credit given for effort rather than merit. Misconceptions or non-relevant concepts.
• y = 2/20:
  Irrelevant discussion/effectively blank.
• z = 0/20:
  Blank.

Grading distribution:
Section 70158
Exam code: midterm1s73W
p: 18 students
r: 12 students
t: 11 students
v: 5 students
x: 4 students
y: 0 students
z: 0 students

A sample "p" response (from student 1776):