## 20150321

### Astronomy quiz question: redshift vs. blueshift

Astronomy 210 Quiz 4, fall semester 2010
Cuesta College, San Luis Obispo, CA

[Version 1]

The (simplified) absorption lines for Iota Sagittarii, a K0 giant, are shown at right. (The arrows indicate the expected wavelength values for a stationary K0 giant.)

Based on its absorption line wavelength values, Iota Sagittarii must be a star:
(A) located a little farther away than 1 parsec.
(B) located closer than 1 parsec.
(C) moving towards Earth.
(D) moving away from Earth.

The absorption lines for Iota Sagittarii are shifted towards slightly larger values ("redshifted"), indicating that it is moving away from Earth.

Section 70158
(A) : 7 students
(B) : 4 students
(C) : 13 students
(D) : 20 students
(No response: 1 student)

"Success level": 47% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.75

[Version 2]

The (simplified) absorption lines for Procyon A, a F5 main sequence star, are shown at right. (The arrows indicate the expected wavelength values for a stationary F5 star.)

Based on its absorption line wavelength values, Procyon A must be a star:
(A) located a little farther away than 1 parsec.
(B) located closer than 1 parsec.
(C) moving towards Earth.
(D) moving away from Earth.

The absorption lines for Procyon A are shifted towards slightly smaller values ("blueshifted"), indicating that it is moving towards Earth.

Section 70160
(A) : 5 students
(B) : 3 students
(C) : 20 students
(D) : 14 students

"Success level": 52% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.82