What information can radial velocity measurements reveal about an extrasolar planet’s orbit?

Radial velocity measurements are a primary method for detecting extrasolar planets by observing the periodic motion of a star as it and its planet orbit their common center of mass. This motion causes a detectable shift in the star's spectral lines due to the Doppler effect.123

Regarding an extrasolar planet's orbit, these measurements reveal the following:

• Orbital Period: The time interval between periodic changes in the star's radial velocity corresponds to the planet's orbital period.12
• Minimum Mass: Because the angle between the planet's orbital plane and the plane of the sky is typically unknown, radial velocity data generally allows astronomers to assign only a minimum mass to the planet.2
• Detection Bias: The method is most effective at detecting planets that are close to their parent stars, as these produce greater and more rapid velocity swings.2

If a planet is also observed to transit its star, the orbital inclination becomes known, which allows for the determination of the planet's actual mass rather than just a minimum value.2