Planetary orbits that are face-on to our line of sight produce no Doppler shift in the stellar spectrum.

Question

Quizplus · Accepted Answer

Doppler shift only occurs when there is motion along the line of sight between the observer and the object being observed. If the planetary orbit is face-on, then there is no motion along the line of sight between the star and the observer, so there will be no Doppler shift in the stellar spectrum.

Planetary Orbits That Are Face-On to Our Line of Sight