The observed spectral lines of a star are all shifted towards the red end of the spectrum. Which statement is true?
A) The star has a radial velocity towards us.
B) The second law of Kirchhoff explains this.
C) The star is not rotating.
D) This is an example of the photoelectric effect.
E) This is an example of the Doppler effect.

Question

Quizplus · Accepted Answer

The redshift of spectral lines indicates that the star is moving away from us, which is an example of the Doppler effect. The Doppler effect describes the change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave source.

The Observed Spectral Lines of a Star Are All Shifted