Calculating galactic space velocities and their uncertainties, with an application to the Ursa Major group

Abstract

Formulas are presented for calculating a star's Galactic space-velocity components U, V, and W from its proper motion, parallax, and radial velocity. The authors also show how to calculate σ<SUB>U</SUB>, σ<SUB>V</SUB>, and σ<SUB>W</SUB> from the uncertainties in the observational quantities. As an example, space velocities are calculated for solar-type stars in the Ursa Major Group, which are then compared to A stars in the nucleus of this cluster and to the broader "supercluster".