Radial velocity (RV) exoplanet detection measures the Doppler wobble of a host star as it is pulled by an unseen companion. High-precision spectrographs like harps and espresso can resolve stellar reflex motion at the sub-m/s level, sensitive to super-Earth and Earth-mass planets around nearby stars.
RV does not directly image the planet or its atmosphere; it yields the planet’s minimum mass (actual mass × sin i), orbital period, and eccentricity. Transits or direct imaging are needed to measure radius and atmosphere. RV’s dominant nuisance source is stellar magnetic activity — spots, faculae, and rotation can mimic planetary signals at similar amplitudes, as happened with gj-887 where a 50-day signal could not be disentangled from the ~39-day stellar rotation until a 2026 campaign resolved both (src-gj-887-d-habitability-2026-03).