Astronomy current events question: comets falling into star HD 172555

Astronomy 210L, spring semester 2017
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!)

Donna Weaver, Ray Villard, and Carol Grady, "Hubble Detects 'Exocomets' Taking the Plunge into a Young Star" (January 6, 2017)
hubblesite.org/news_release/news/2017-02

The Hubble Space Telescope detected evidence of comets falling into star HD 172555, based on observations of:
(A) flickering star brightnesses.
(B) a young gas-giant planet.
(C) rapidly moving gaseous debris.
(D) ice crystal reflections.
(E) comet tail formation.

Correct answer: (C)

Student responses
Sections 30679, 30680
(A) : 7 students
(B) : 7 students
(C) : 13 students
(D) : 3 students
(E) : 3 students