20101211

Astronomy quiz question: IAU classification scheme (1)

Astronomy 210 Quiz 7, Fall Semester 2010
Cuesta College, San Luis Obispo, CA

Listed below are the minimal qualifications established by the International Astronomical Union for a planet:

I. Orbits the sun.
II. Shape "rounded-out" by gravity.
III. Cleared/dominates orbit around sun.

Of the following choices, which solar system object(s) meets only qualification II?
(A) Earth's moon.
(B) Ceres, a dwarf planet.
(C) Ida, an asteroid.
(D) Mercury.
(E) (More than one of the above choices.)
(F) (None of the above choices.)

Correct answer: (A)

Earth's moon is round in shape, but does not directly orbit the sun (it orbits Earth, which itself orbits the sun); and also Earth's moon does not dominate its orbit around the sun.

Section 70160
(A) : 25 students
(B) : 4 students
(C) : 5 students
(D) : 0 students
(E) : 5 students
(F) : 0 students

"Success level": 67% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.64

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