Radial Velocity (RV) is the component of velocity of a body on a line between the body and the observer, i.e., the movement toward or away from the observer. A star's radial velocity can be determined by measuring the Doppler Shift of known Spectral Lines (Spectral Radial Velocity), which can be used to identify the presence of Extra-Solar Planets and Binary Stars. Observatories with instruments designed to determine radial velocities are sometimes referred to as RV Observatories (Radial Velocity Observatories).
Measuring changes in radial velocity over time is helpful for detecting planets with small (a day or few days) or medium (1-2 AU) orbits (The Radial Velocity Method or RV Method of exoplanet detection), but Transits reveal more of the smaller orbits. Using the RV Method requires HRS, which, in turn, requires a degree of brightness (Apparent Magnitude of 12 or brighter) and currently measures down to about one meter/second precision. 1/10 meter/second would be required to detect Earth.
Velocity Dispersion (σ)
Double-Line Spectroscopic Binary
55 Cancri e (55 Cnc e)
Galactic All-Sky Survey (GASS)
HD 209458 b
HD 80606 b
Hot Jupiter (HJ)
Keck Planet Finder (KPF)
Lick Observatory Calcium Line Survey (LkCl)
Local Standard of Rest (LSR)
Position-Position-Velocity Space (PPV)
Sloan Digital Sky Survey (SDSS)
Stellar Mass Determination
Telescopio Nazionale Galileo (TNG)