As the planet moves around the star, the star has a reflex motion . The reflex motion can cause the star to wiggle on the sky. Less massive stars display a larger motion but will have longer periods. 10 -4 arcsec possible with Keck Doppler Spectroscopy Illustration Doppler Spectroscopy Reflex motion of the star results in a Doppler shift which is best seen edge on. The angular separation between planets and the star is larger.
Conclusions Searching for planets is a tough, time consuming task.