stellar motion

Stellar motion refers to how stars move through space. Astronomers measure this movement in two primary ways: proper motion and radial velocity. Proper motion tracks a star's movement across the sky, perpendicular to our line of sight, and is measured in arc seconds per year. Radial velocity measures a star's motion directly toward or away from us along the line of sight, determined by shifts in its spectral lines due to the Doppler effect.123

Combining these measurements, along with a star's parallax (distance), allows astronomers to calculate its total space motion. Some stars, known as high-velocity stars, exhibit exceptionally large velocities relative to the Sun. The Sun itself is also in motion, orbiting the center of the Milky Way Galaxy.214