## 20101017

### Astronomy midterm question: morning star Saturn?

Astronomy 210 Midterm 1, Fall Semester 2010
Cuesta College, San Luis Obispo, CA

[20 points.] Consider a popular online search (wordnetweb.princeton.edu) result for the definition of "morning star":
A planet (usually Venus) seen just before sunrise in the eastern sky.
--http://wordnetweb.princeton.edu/perl/webwn?s=morning%20star
Discuss whether it is possible or impossible for Saturn to also be a morning star, under this definition. Support your answer using a diagram showing the positions of the sun, Saturn, Earth, and an observer on Earth.

Solution and grading rubric:
• p = 20/20:
Correct. Discusses the possibility of Saturn being in the eastern sky just before (or at) sunrise by drawing a heliocentric diagram with Saturn orbit larger than Earth's orbit, with Saturn near the opposite side of the sun (i.e., just after Earth and Saturn at conjunction), making Saturn visible to a morning observer, (slightly) higher above the same horizon as the rising sun.
• r = 16/20:
Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Draws Saturn at or just past conjunction, which would place it low in the eastern horizon at sunrise, but claims impossible to see due to brightness of the sun, or generally indicates where Saturn must be located along its orbit to be visible at sunrise, but does not sufficiently place near the eastern horizon.
• t = 12/20:
Contains right ideas, but discussion is unclear/incomplete or contains major errors. Argues possibility or impossibility based on a diagram showing Saturn visible in the western horizon at sunrise, or visible in the eastern horizon at sunset.
• v = 8/20:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Problematic diagram with Earth's orbit inside of Venus, Saturn's orbit inside of Earth's.
• 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.
Grading distribution:
Section 70160
p: 33 students
r: 1 student
t: 3 students
v: 3 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 3363):