Astronomy quiz question: absolute magnitude of Eta Aurigae from apparent magnitude, distance

Astronomy 210 Quiz 5, fall semester 2016
Cuesta College, San Luis Obispo, CA

Eta Aurigae is a star with an apparent magnitude of m = +3.2, and is located 75 parsecs from Earth. Eta Aurigae has an absolute magnitude M of:
(A) –1.2.
(B) +3.2.
(C) +4.4.
(D) Not enough information is given.)

Correct answer (highlight to unhide): (A)

Eta Aurigae appears to have a brightness of +3.2 as seen from its true distance of 75 parsecs from Earth, but when placed at the "fair" distance of 10 parsecs away (where it would have its "fair brightness" or absolute magnitude), Eta Aurigae would become brighter.

(Response (B) is the same magnitude as the given apparent magnitude; response (C) is dimmer than the given apparent magnitude.)

Section 70158
Exam code: quiz05s4nD
(A) : 19 students
(B) : 3 students
(C) : 2 students
(D) : 13 student

Success level: 54% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.30

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