Astronomy quiz question: IAU classification scheme for comets, asteroids

Astronomy 210 Quiz 7, Spring Semester 2010
Cuesta College, San Luis Obispo, CA

[Version 1]

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.

Which of these qualifications are met by a comet?
(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) (None of the above choices.)

Section 30674
(A) : 23 students
(B) : 5 students
(C) : 0 students
(D) : 5 students
(E) : 1 student
(F) : 1 student
(G) : 6 students

Correct answer: (A)

Comets are typically irregularly shaped, and have eccentric and tilted orbits around the sun, and thus they have not cleared out nor dominate their orbits.

"Success level": 59% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.82

[Version 2]

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.

Which of these qualifications are met by an asteroid?
(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) (None of the above choices.)

Section 30676
(A) : 23 students
(B) : 5 students
(C) : 3 students
(D) : 16 students
(E) : 5 students
(F) : 6 students
(G) : 2 students

Correct answer: (A)

Asteroids orbit the sun, typically between Mars and Jupiter. However, they are irregularly shaped (if they were spherical, they would be dwarf planets), and they have not cleared out nor dominate their orbits (if they did, they would be planets).

This quiz question was also given in Fall semester 2008.

"Success level": 46% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.60