## 20191018

### Astronomy quiz question: meeting only the first and second IAU planetary qualifications

Astronomy 210 Quiz 4, fall semester 2019
Cuesta College, San Luis Obispo, CA

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.
Of the following choices, which solar system object(s) meets only qualifications I and II?
(A) Earth's moon.
(B) Ceres (a spherical-shaped body in the asteroid belt).
(C) Ida (an irregular-shaped body in the asteroid belt).
(D) Mercury.
(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): (B)

The moon orbits Earth (and does not directly orbit the sun, failing qualification I); is "rounded out" in shape (meeting qualification II); and does not dominate its orbit around the sun (failing qualification III), as it is gravitationally bound to orbiting Earth as Earth orbits the sun.

Ceres orbits the sun (meets I); is "rounded out" in shape (meets II); but does not dominate its orbit around the sun, sharing it with other asteroid belt objects (fails III).

Ida orbits the sun (meets I); is irregular in shape (fails II); and does not dominate its orbit around the sun (fails III); and does not dominate its orbit around the sun, sharing it with other asteroid belt objects (fails III).

Mercury orbits the sun (meets I); its shape is "rounded out" (meets II); and dominates its orbit around the sun, not sharing it with any other object (meets III).

Thus Ceres is the only one of these choices that only meets qualifications I and II, but does not meet qualification III.

Section 70160
Exam code: quiz04NDme
(A) : 2 students
(B) : 7 students
(C) : 0 students
(D) : 1 student
(E) : 5 students
(F) : 0 students
(G) : 8 students

Success level: 35% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.50

#### 1 comment:

Patrick M. Len said...

Astronomy 210 Quiz 7, fall semester 2010
Cuesta College, San Luis Obispo, CA

Section 70158
Exam code: quiz07sA7r
(A) : 1 student
(B) : 28 students
(C) : 4 students
(D) : 3 students
(E) : 4 students
(F) : 0 students
(G) : 2 students
(No response: 1 student)

Success level: 67% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.58