radial velocity


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The line-of-sight velocity of a star or other celestial object towards or away from an observer. Astronomers can calculate the radial velocity of a celestial objects by recording a spectrum with a spectrograph and measuring the Doppler shift of several spectral lines. Measurements of radial velocity have revealed how our Solar System moves through space and orbits the center of our galaxy. Astronomers have also used radial velocity measurements to observe that most objects beyond our galaxy travel away from us at speeds that increase with the object's distance.