Astronomy quiz question: Lagoon Nebula colors

Astronomy 210 Quiz 6, spring semester 2016
Cuesta College, San Luis Obispo, CA

"eso1403a (VST images the Lagoon Nebula)"
ESO/VPHAS+ team
eso.org/public/usa/images/eso1403a/

[Version 1] The Lagoon Nebula (Messier 8/NGC 6523) is observed to have regions of pink and dark brown colors. The composition of its pink color regions is:
(A) helium gas.
(B) hydrogen gas.
(C) very small dust particles.
(D) dense clumps of large dust particles.

Correct answer (highlight to unhide): (B)

The pink colors are the combination of red, violet, and blue photons given off by excited hydrogen electrons jumping down to lower orbitals.

Section 30674
Exam code: quiz06ncM7
(A) : 4 students
(B) : 9 students
(C) : 7 students
(D) : 0 students

Success level: 48% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.20

[Version 2] The Lagoon Nebula (Messier 8/NGC 6523) is observed to have regions of pink and dark brown colors. The composition of its dark brown color regions is:
(A) helium gas.
(B) hydrogen gas.
(C) very small dust particles.
(D) dense clumps of large dust particles.

Correct answer (highlight to unhide): (D)

The dark brown color is due to large, clumpy dust particles blocking visible light.

Section 30676
Exam code: quiz06sRR0
(A) : 1 student
(B) : 5 students
(C) : 7 students
(D) : 35 students

Success level: 74% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.29