I want to know the velocity of a star, like Sirius or something. How would I find it?

I want to know the velocity of a star, like Sirius or something. How would I find it using the proper motion and the radial motion of the velocity?|||Google the star by name or look it up in Wikipedia. Odds are you will only find the radial velocity relative to Earth, which is based on Doppler shift of the star's spectrum.





Tangential velocity is more difficult to measure. For example, Wikipedia lists the radial velocity of Serious as -7.6 km/s. That's about 1.6 AU/y. Sirius is 2.64 ps from Earth, so a tangential velocity of 1.6 AU/y would be about 1.6/2.64 = .6"/y or 1'/century. After measuring the change of direction relative to distant galaxies, we would have to take into account all the other relative motions, like orbiting the galaxy.|||If you know the translational velocity and radial velocity, the 3-D velocity is





V = 鈭歔Vr虏+Vt虏]|||First decide what you would compare it to. Its speed would have to be measured against something else, since it is a relative motion.