-The above visual wavelength image of spectra (right panel) taken from a spiral galaxy (left panel) shows an emission line that is__________ on the side that is rotating away and an emission line that is ___________ on the side that is rotating towards us.

Question

Quizplus · Accepted Answer

The emission line is redshifted on the side of the galaxy that is rotating away from us due to the Doppler effect, which stretches the wavelengths of light to longer (redder) wavelengths. Conversely, the emission line is blueshifted on the side rotating towards us, as the Doppler effect compresses the wavelengths of light to shorter (bluer) wavelengths.

-The Above Visual Wavelength Image of Spectra (Right Panel) Taken