high-velocity starsVery old (population II) stars in the galactic halo that are relatively near the Sun but do not share in the common circular motion around the galactic center of the Sun and other stars in the Sun's neighborhood (see local standard of rest). They are actually moving slower than the Sun in elliptical orbits that often carry them far out of the galactic plane. Their apparently high velocities (>65 km s–1) relative to the Sun result from this difference in relative motions. High velocity provides an easy means of identifying individual old stars near the Sun, i.e. stars with a low abundance of heavy elements.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006