Astronomy multiple-choice question: Amalthea and IAU classification scheme

Astronomy 210 Quiz 7, fall semester 2011
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.
Amalthea, an asteroid, was captured by Jupiter and became its satellite. Which qualification(s) changed when this happened?
(A) I only.
(B) II only.
(C) III only.
(D) Both I and II.
(E) Both II and III.
(F) Both I and III.
(G) I, II, and III.
(H) (None of the above choices.)

Correct answer: (A).

Amalthea, while an asteroid, orbited the sun (met qualification I), but did not clear/dominate its orbit around the sun in the asteroid belt (did not meet qualification III). When captured by Jupiter to become its satellite, qualification I changed, as now it no longer orbits the sun. Even though the shape of Amalthea was not discussed, it would not have changed when captured by Jupiter.

Section 70158
Exam code: quiz07s3tI
(A) : 9 students
(B) : 2 students
(C) : 6 students
(D) : 4 students
(E) : 2 students
(F) : 2 students
(G) : 2 students
(H) : 4 students

Success level: 35% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.48

Section 70160
Exam code: quiz07n0N3
(A) : 15 students
(B) : 4 students
(C) : 3 students
(D) : 2 students
(E) : 0 students
(F) : 3 students
(G) : 0 students
(H) : 1 student

Success level: 57% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.38

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