Stars only exhibit a Doppler shift if they are moving

Question

Quizplus · Accepted Answer

The Doppler effect occurs when there is relative motion between the source (star) and the observer (us). The apparent frequency of the waves changes as the source moves toward or away from the observer, causing a shift in the wavelength. This can only occur if the star is moving either toward or away from us along the line of sight. Therefore, options A and B can be eliminated. Option C is also incorrect because circular motion does not necessarily involve changes in distance between the star and us, which are required for Doppler shift.

Stars Only Exhibit a Doppler Shift If They Are Moving