Astronomy quiz question: IAU classification scheme (2)

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 qualifications I and 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: (B)

Ceres directly orbits the sun (it is not a satellite of a planet), is round in shape, but does not dominate its orbit in the asteroid belt around the sun.

Section 70158
(A) : 1 student
(B) : 28 students
(C) : 4 students
(D) : 3 students
(E) : 4 students
(F) : 2 students
(No response: 1 student)

"Success level": 67% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.58

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