The apparent angular motion of a star across the sky over time, measured in arcseconds per year, reflecting the star's actual movement through space relative to the solar system. This motion is perpendicular to our line of sight to the star.
The term 'proper' comes from Latin 'proprius' meaning one's own or intrinsic, distinguishing this real stellar motion from apparent motions caused by Earth's rotation or orbit. First systematically studied by Edmond Halley in 1718 when he noticed stars had moved since ancient times.
Proper motion reveals that our seemingly fixed stars are actually racing through space at incredible speeds! Barnard's Star moves so fast that in just 180 years, it travels a distance equal to the Moon's apparent diameter across our sky.
Complete word intelligence in one call. Free tier — 50 lookups/day.