Radial Velocities of Binary Stars

During its orbit around the center of mass of the binary system, a star's radial velocity (the velocity component along the line of sight, towards or away from us) varies systematically (if the binary system is not observed exactly perpendicular to the line of sight).

The ratio of the maximum radial velocities of the two stars is inversely proportional to the ratio of their masses. The less massive star moves faster than the more massive one.

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