The planet was proposed through the radial velocity method, the most common planet-hunting technique. A "wobble" observed in Barnard's Star's motion was confirmed to have a period of about 233 days, corresponding to a semi-major axis of 0.4 AU for a proposed companion. The mass of the likely planetary body was then deduced to be about 3.2 Earth mass. Lead astronomer Ignasi Ribas notes: "We used observations from seven different instruments, spanning 20 years of measurements, making this one of the largest and most extensive datasets ever used for precise radial-velocity studies."
