Astronomy quiz question: IAU classification of 588 Achilles

Astronomy 210 Quiz 4, spring semester 2016
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.
Achilles is described as an irregularly-shaped object that shares Jupiter's orbit, always leading Jupiter as they both orbit the sun[*]. According to the IAU qualifications, Achilles is classified as:
(A) a moon.
(B) solar system debris.
(C) a dwarf planet.
(D) a planet.
(E) (None of the above choices.)

[*] wki.pe/588_Achilles.

Correct answer (highlight to unhide): (B)

Achilles directly orbits the sun (meeting qualification I), but its shape is not "rounded out," and because it fails qualification II, Achilles is categorized as solar system debris.

Section 30674
Exam code: quiz04nG4N
(A) : 1 student
(B) : 15 students
(C) : 1 student
(D) : 0 students
(E) : 2 students

Success level: 80% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.40

Section 30676
Exam code: quiz04stP7
(A) : 7 students
(B) : 29 students
(C) : 9 students
(D) : 1 student
(E) : 3 students

Success level: 62% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.33

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