Astronomy current events question: mass of Kleopatra

Astronomy 210L, Spring Semester 2011
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!)

Emily Lakdawalla, "A Dog-Bone-Shaped Asteroid's Two Moons: Kleopatra, Cleoselene, and Alexhelios," February 23, 2011
http://www.planetary.org/blog/article/00002926/

The mass and density of asteroid Kleopatra (216) was recently determined by:
(A) observing its collision with a smaller asteroid.
(B) timing reflected laser light pulses from the KECK II Telescope.
(C) the impact crater size created by NASA's Stardust-NexT spacecraft.
(D) calculating the volume of its unusual dog-bone shape.
(E) measurements of the orbits of its two moons.

Correct answer: (E)

Student responses
Sections 30678, 30679, 30680
(A) : 7 students
(B) : 5 students
(C) : 4 students
(D) : 12 students
(E) : 27 students