Astronomy quiz question: absolute magnitude of Altair from apparent magnitude, distance

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

Altair is a star with an apparent magnitude of m = +0.8, and is located 5.1 parsecs from Earth. Altair has an absolute magnitude M of:
(A) –3.0.
(B) +0.8.
(C) +2.2.
(D) Not enough information is given.)

Correct answer (highlight to unhide): (C)

Altair appears to have a brightness of +0.8 as seen from its actual location of 5.1 parsecs from Earth, but when placed at the "fair" distance of 10 parsecs away (where it would have its "fair brightness" or absolute magnitude), Altair would become dimmer.

(Response (A) is brighter than the given apparent magnitude; response (B) is the same magnitude as the given apparent magnitude.)

Section 70160
Exam code: quiz05n0Ko
(A) : 6 students
(B) : 1 student
(C) : 11 students
(D) : 7 student

Success level: 49% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.63

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