## 20180329

### Astronomy quiz question: comparing brightnesses of stars moved to 10 parsecs away

Astronomy 210 Quiz 5, spring semester 2018
Cuesta College, San Luis Obispo, CA

The apparent magnitudes and absolute magnitudes of two stars are listed below.
 mapparentmagnitude Mabsolutemagnitude Tureis +2.8 +1.4 Beta Hydri +2.8 +3.5

If both Tureis and Beta Hydri are moved to 10 parsecs away from Earth, __________ will be appear to be brighter in the night sky, as seen from Earth.
(A) Tureis.
(B) Beta Hydri.
(C) (There is a tie.)
(D) (Not enough information is given.)

Correct answer (highlight to unhide): (A)

The absolute magnitude of a star is the brightness it has when placed 10 parsecs away from Earth. Since Tureis has an absolute magnitude of +1.4 that is brighter than Beta Hydri's absolute magnitude of +3.5, if both stars were placed 10 parsecs away from Earth, Tureis will appear to be brighter in the night sky.

Section 30674
Exam code: quiz05NoPw
(A) : 16 students
(B) : 2 students
(C) : 1 student
(D) : 0 students
(No responses: 1 student)

Success level: 86% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.60

Section 30676
Exam code: quiz05So1L
(A) : 34 students
(B) : 7 students
(C) : 1 student
(D) : 0 students

Success level: 82% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.64