Astronomy quiz question: possible dwarf planet IAU classification of Chiron

Astronomy 210 Quiz 4, spring semester 2015
Cuesta College, San Luis Obispo, CA

Refer below to 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.
Chiron is an object with an unstable orbit around the sun that passes close to Jupiter's and Uranus' orbit[*], and as of March 2015 is listed as a "possible" dwarf planet.[**] In order to officially qualify as a dwarf planet, Chiron's __________ must be confirmed.
(A) rounded shape.
(B) orbital stability.
(C) influence on solar system debris.
(D) (None of the above choices would confirm Chiron as a dwarf planet.)

[*] http://en.wikipedia.org/wiki/2060_Chiron.
[**] http://web.gps.caltech.edu/~mbrown/dps.html.

Correct answer (highlight to unhide): (A)

Chiron orbits the sun directly, so it is not a moon. If it were irregular in shape, it would classified as solar system debris. However, if Chiron were rounded in shape, it would then be classified as a dwarf planet, as it does not dominate its orbit around the sun.)

Section 30676
Exam code: quiz04s0U7
(A) : 29 students
(B) : 14 students
(C) : 3 students
(D) : 1 student

Success level: 64% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.46

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