Astronomy current events question: dwarf planet candidate 2015 RR245

Astronomy 210L, fall semester 2016
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!)

Kenneth Chang, "Astronomers Discover New Likely Dwarf Planet, the Latest of Many" (July 13, 2016)
nytimes.com/2016/07/14/science/astronomers-discover-new-likely-dwarf-planet.html

The size of dwarf planet candidate 2015 RR245 was estimated from measurements of its _________ by the Canada-France-Hawaii Telescope.
(A) gravitational pull on Pluto.
(B) rotation rate.
(C) brightness and distance.
(D) orbiting moons.
(E) cryovolcanic activity.

Correct answer: (C)

Student responses
Sections 70178, 70186
(A) : 5 students
(B) : 5 students
(C) : 17 students
(D) : 1 student
(E) : 2 students