 Proper motion

Proper motion is the astrometric measure of the observed changes in the apparent places of stars or other celestial objects in the sky, as seen from the center of mass of the Solar System, compared to the abstract background of the more distant stars.The components for proper motion in the equatorial coordinate system (of a given epoch, often J2000.0) are given in the direction of right ascension ("μ"α) and of declination ("μ"δ).