If you look a star up in Wikipedia it will usually give the star's
proper motion and
radial velocity. The radial velocity is what you are asking.
http://en.wikipedia.org/wiki/Proxima_Centauri
Quote:
Radial velocity (Rv) −21.7 ± 1.8[2] km/s <----------
Proper motion (μ) RA: −3775.40[1] mas/yr
Dec.: 769.33[1] mas/yr
Parallax (π) 768.7 ± 0.3[3] mas
Distance 4.243 ± 0.002 ly
(1.3009 ± 0.0005 pc)
Absolute magnitude (MV) 15.49[4]
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http://en.wikipedia.org/wiki/Radial_velocity
http://en.wikipedia.org/wiki/Proper_motion