Planetary masses measured using the Doppler technique are lower limits to the possible planetary mass.

Question

Quizplus · Accepted Answer

This is because the Doppler technique measures the reflex motion of the star caused by the gravitational pull of the orbiting planet. The measured velocity amplitude is related to the planet's mass, but only if we know the inclination of the planet's orbit relative to our line of sight. If the orbit is close to face-on, the true mass of the planet will be larger than the measured mass, while if the orbit is close to edge-on, the true mass will be close to the measured mass. Therefore, the measured mass represents a lower limit to the true mass.

Planetary Masses Measured Using the Doppler Technique Are Lower Limits