Astronomy quiz question: stellar distances

Astronomy 10 Quiz 8, Spring Semester 2008
Cuesta College, San Luis Obispo, CA

Astronomy 10 learning goal Q8.4

[Version 1]

Which one of the following choices best corresponds to an absolute magnitude +3 star that is the farthest away from the Earth?
(A) A star with an apparent magnitude of –6.
(B) A star with an apparent magnitude of –3.
(C) A star with an apparent magnitude of 0.
(D) A star with an apparent magnitude of +3.
(E) A star with an apparent magnitude of +6.

Correct answer: (E).

Out of the above (A)-(E) choices, the star with a +6 apparent magnitude appears to be the dimmest, as seen from the Earth. Thus a star with a given absolute magnitude value (here, +3) would be farthest away if it appeared to be as dim as possible.

Student responses
Section 4160
(A) : 4 students
(B) : 3 students
(C) : 0 students
(D) : 1 students
(E) : 8 students

Section 5166
(A) : 4 students
(B) : 2 students
(C) : 1 student
(D) : 3 students
(E) : 13 students

[Version 2]

Which one of the following choices best corresponds to an absolute magnitude +3 star that is the closest to the Earth?
(A) A star with an apparent magnitude of –6.
(B) A star with an apparent magnitude of –3.
(C) A star with an apparent magnitude of 0.
(D) A star with an apparent magnitude of +3.
(E) A star with an apparent magnitude of +6.

Correct answer: (A).

Out of the above (A)-(E) choices, the star with a -6 apparent magnitude appears to be the brightest, as seen from the Earth. Thus a star with a given absolute magnitude value (here, +3) would be nearest if it appeared to be as bright as possible.

Student responses
Section 4160
(A) : 6 students
(B) : 5 students
(C) : 3 students
(D) : 2 students
(E) : 3 students

Section 5166
(A) : 16 students
(B) : 2 students
(C) : 3 students
(D) : 3 students
(E) : 3 students