Astronomy current events question: SDSS 1557's metal-rich asteroids

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!)

Bex Caygill, "First Evidence of Rocky Planet Formation in Tatooine System" (February 27, 2017)
ucl.ac.uk/news/news-articles/0217/270217-First-evidence-of-rocky-planet-formation-in-Tatooine-system

The SDSS 1557 system's white dwarf and brown dwarf may be orbited by shattered metal-rich asteroids, based on measurements of:
(A) Doppler shifts.
(B) gravitational wobbles.
(C) magnetic field strengths.
(D) brightness fluctuations.
(E) absorbed light wavelengths.

Correct answer: (E)

Student responses
Sections 30679, 30680
(A) : 2 students
(B) : 3 students
(C) : 8 students
(D) : 6 students
(E) : 13 students