20141101

Astronomy quiz question: IAU classification of Styx

Astronomy 210 Quiz 4, fall semester 2014
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.
Pluto is orbited by Styx, which is smaller and "estimated to be irregular in shape."[*] According to the IAU qualifications, Styx is classified as:
(A) a moon.
(B) solar system debris.
(C) a dwarf planet.
(D) a planet.
(E) (None of the above choices.)

[*] http://hubblesite.org/newscenter/archive/releases/2012/32/full/.

Correct answer (highlight to unhide): (A)

Qualification I is not met by Styx, as it orbits Pluto instead of orbiting the sun directly, making Styx a moon. This is regardless of shape, as the first "no" answer to the International Astronomical Union criteria classifies it as a moon.

Section 70158
Exam code: quiz04s4tR
(A) : 16 student
(B) : 22 students
(C) : 5 students
(D) : 0 students
(E) : 1 student

Success level: 41% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.86

Section 70160
Exam code: quiz04n33P
(A) : 12 student
(B) : 16 students
(C) : 7 students
(D) : 0 students
(E) : 0 students

Success level: 38% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.50

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