Radial Velocity Method

Detecting exoplanets by measuring the wobble of a star caused by the gravitational pull of an orbiting planet.

Also known as the Doppler method, radial velocity detection measures tiny shifts in the wavelength of a star's light caused by the gravitational tug of an orbiting planet. As the planet orbits, it pulls the star slightly toward and away from us, creating a periodic redshift and blueshift in the star's spectrum. The size of the wobble reveals the planet's minimum mass, while the period reveals the orbital distance. This was the first successful method for detecting exoplanets around Sun-like stars and remains one of the most important techniques, particularly for measuring planet masses.