Astronomy 210 Final Exam, Fall Semester 2008
Cuesta College, San Luis Obispo, CA
[4.0 points.] ε Eridani is a star that has an apparent magnitude m = +3.72 and an absolute visual magnitude M_V = +6.2. Approximately how far away is ε Eridani from Earth?
(A) Much farther away than 10 parsecs.
(B) A little farther away than 10 parsecs.
(C) Exactly 10 parsecs away.
(D) Closer than 10 parsecs away.
Section 70160
(A) : 6 students
(B) : 3 students
(C) : 0 students
(D) : 13 students
Correct answer: (D)
When brought to the "fair distance" of 10 parsecs (thus changing its apparent magnitude to absolute visual magnitude), ε Eridani now seems to be dimmer, indicating that it must have moved away to the Earth during this process. Thus ε Eridani must be closer than this fair distance of 10 parsecs.
"Difficulty level": 73%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.50
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