Fr.: mouvement propre
The apparent motion of a star across the sky (not including a star's parallax), arising from the star's velocity through space with respect to the Sun. Proper motion is usually tabulated in star catalogs as changes in right ascension and declination per year or century. See also: → proper motion distance.
proper motion distance
durâ-ye jonbeš-e saré
Fr.: distance mouvement propre
The distance derived from the → proper motion of an object. If an object has a known → transverse velocity u, and has an observed angular motion of dθ/dt, then the proper motion distance is defined as: d = u/(dθ/dt).