Astronomy clicker question: extrasolar planet orbits

Astronomy 10, Spring Semester 2008
Cuesta College, San Luis Obispo, CA

Astronomy 10 learning goal Q7.5

Students were asked the following clicker question (Classroom Performance System, einstruction.com) in the middle of their learning cycle:

[0.3 points.] How did "extrasolar" giant planets in small, eccentric orbits form?
(A) They were formed very close to their stars, in eccentric orbits.
(B) They were formed very far from their stars, in circular orbits, but their orbits were disrupted by collisions with other protoplanets, and spiraled inwards.
(C) They were formed very far from their stars, in circular orbits, but they lost angular momentum to the protoplanetary disk, and spiraled inwards.
(D) They were produced by material ejected from a collision between two stars.

Correct answer: not revealed yet (see discussion below).

Student responses
Section 4160
(A) : 0 students
(B) : 20 students
(C) : 4 students
(D) : 1 student

Section 5166
(A) : 11 students
(B) : 8 students
(C) : 7 students
(D) : 6 students

The students in section 4160 chose impacts on protoplanets (response (B)) over the correct response (C) of (gradual) angular momentum redistribution, after a discussion earlier in the same lecture about angular momentum transfer from the young Sun to its nebular disk. This prompted a refresher on this same subject immediately afterwards.

In section 5166, after showing the lack of consensus in their replies, students were asked to discuss their responses with each other before responding again, with a moderate shift towards the correct answer.

Student responses
Section 5166
(A) : 8 students
(B) : 8 students
(C) : 13 students
(D) : 3 students

Correct answer: (C)