Astronomy current events question: Kepler-9 planetary transits

Astronomy 210L, Fall Semester 2010
Cuesta College, San Luis Obispo, CA

Students are assigned to read online articles on current astronomy events, and take a short current events quiz during the first 10 minutes of lab. (This motivates students to show up promptly to lab, as the time cut-off for the quiz is strictly enforced!)

Alan MacRobert, "Two Exoplanets in an Interactive Dance," August 26, 2010
http://www.skyandtelescope.com/news/101571373.html

How have NASA researchers determined that two planets orbiting the sun-like star Kepler 9 are gravitationally interacting with each other?
(A) Both planets are moving farther out away from their star.
(B) The time for each planet to pass in front of their star changes slightly.
(C) One planet loses hydrogen, while the other gains hydrogen.
(D) Predictions from Einstein's general theory of relativity.
(E) The star's rotation rate changes slightly.

Correct answer: (B)

Student responses
Sections 70178, 70186, 70200
(A) : 3 students
(B) : 46 students
(C) : 4 students
(D) : 0 students
(E) : 11 students