Radial velocity

Radial velocity is an object's speed component toward or away from an observer along the line of sight. It is commonly inferred from Doppler shifts in spectral lines.

Doppler effect: The change in observed wave frequency caused by relative motion between a source and an observer. Relative motion shifts spectral lines, revealing an object's radial motion.
Radial velocity method: An exoplanet detection technique that infers a planet from its gravitational wobble of a star. Periodic stellar radial-velocity shifts can reveal an orbiting planet.
Electromagnetic spectrum: The full range of electromagnetic radiation, ordered by frequency or wavelength. Spectroscopic radial velocities are inferred from shifts within this range.
Transverse velocity: The component of an object's velocity perpendicular to the line of sight. It describes motion across the sky rather than toward or away from the observer.
Doppler spectroscopy: A technique that measures motion by tracking Doppler shifts in an object's spectrum. It is the principal spectroscopic method for measuring radial velocity.
Exoplanet: A planet orbiting a star beyond the Solar System. An exoplanet can be detected through the radial motion it induces in its host star.
Wavelength: The distance between successive corresponding points of a wave. Radial-velocity measurements compare observed wavelengths with known rest wavelengths.
Peculiar velocity: An object's velocity relative to the average motion of its surrounding system or cosmic expansion. It separates local motion from recession associated with cosmic expansion.
Redshift: An increase in a wave's observed wavelength relative to its emitted wavelength. Receding objects show redshift in their spectral lines.
Binary star: A star system whose two stars orbit their shared center of mass. Orbital motion produces changing radial velocities that expose spectroscopic binaries.

Linked from 20 pages