20180322

Astronomy quiz question: only meeting the last IAU planetary qualification

Astronomy 210 Quiz 4, spring semester 2018
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.
Which solar system object(s) only meets qualification III, but does not meet qualifications I and II?
(A) Mercury.
(B) Makemake, a dwarf planet.
(C) Hermione, an irregular-shaped asteroid.
(D) Io, a moon of Jupiter with active sulfur volcanoes.
(E) (More than one of the above choices.)
(F) (All of the above choices.)
(G) (None of the above choices.)

Correct answer (highlight to unhide): (G)

Mercury orbits the sun (meeting qualification I); is "rounded out" in shape (meeting qualification II); and gravitationally dominates its orbit around the sun (meeting qualification III).

Makemake orbits the sun (meeting qualification I); is "rounded out" in shape (meeting qualification II); but does not gravitationally dominate its orbit around the sun, sharing it with other Kuiper Belt objects (failing qualification III).

Hermione orbits the sun (meeting qualification I; but is irregular in shape (failing qualification II); and does not gravitationally dominate its orbit around the sun, sharing it with other asteroids (failing qualification III).

Io orbits Jupiter (and does not directly orbit the sun, failing qualification I); is round in shape (meeting qualification II); and does not dominate its orbit around the sun (failing qualification III), as it is gravitationally bound to orbiting Jupiter as Jupiter orbits the sun.

Thus none of these objects listed here does not meet qualifications I and II, but meets qualification III.

Section 30674
Exam code: quiz04NCh4
(A) : 1 student
(B) : 3 students
(C) : 6 students
(D) : 3 students
(E) : 1 student
(F) : 0 students
(G) : 9 students

Success level: 43% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 1.00

Section 30676
Exam code: quiz04sLrW
(A) : 2 students
(B) : 6 students
(C) : 11 students
(D) : 3 students
(E) : 3 students
(F) : 0 students
(G) : 13 students

Success level: 37% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.63

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