20170323

Astronomy quiz question: IAU classification of irregularly-shaped(?) Chariklo

Astronomy 210 Quiz 4, spring semester 2017
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.
Chariklo is an object that has an unstable orbit around the sun, directly influenced by Uranus' gravity. Chariklo is surrounded by two rings (nicknamed "Oiapoque" and "Chuí"), and probably has at least one small moon still waiting to be discovered. The exact shape of Chariklo is not yet completely known. According to the IAU qualifications, if Chariklo is found to have an irregular shape, it would be classified as:
(A) a moon.
(B) solar system debris.
(C) a dwarf planet.
(D) a planet.
(E) (None of the above choices.)

[*] eso.org/public/news/eso1410/.

Correct answer (highlight to unhide): (B)

Chariklo directly orbits the sun (meeting qualification I), but with an irregular shape, it would not satisfy qualification II, classifying it as solar system debris. It also does not satisfy qualification III (as it is directly influenced by Uranus' gravity), but this does not affect its solar system debris classification. (If Chariklo had a spherical shape, then it would meet both qualifications I and II, while not meeting qualification III, which would then classify it as a dwarf planet.)

Section 30674
Exam code: quiz04nqyL
(A) : 1 student
(B) : 21 students
(C) : 0 students
(D) : 0 students
(E) : 1 student

Success level: 92% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.17

Section 30676
Exam code: quiz04sl4M
(A) : 1 student
(B) : 35 students
(C) : 1 student
(D) : 0 students
(E) : 2 students
(No response: x students)

Success level: 91% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.25

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