Astronomy 210 Quiz 2, Fall Semester 2008
Cuesta College, San Luis Obispo, CA
[4.0 points.] Why are Mercury and Venus never visible in the San Luis Obispo, CA sky at midnight?
(A) Mercury and Venus never exhibit retrograde motion.
(B) Mercury and Venus are too small to reflect enough sunlight.
(C) The orbits of Mercury and Venus are smaller than the orbit of the Earth.
(D) Mercury and Venus cannot exhibit gibbous phases.
Correct answer: (C)
Since the orbits of Mercury and Venus are smaller than the orbit of the Earth (making them inferior planets), they can never appear behind the Earth, with respect to the Sun, and thus cannot be overhead (or anywhere in the sky) at midnight for typical temperate latitudes such as for San Luis Obispo, CA.
Student responses
Section 70158
(A) : 9 students
(B) : 3 students
(C) : 42 students
(D) : 4 students
"Difficulty level": 75%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.76
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