# space velocity

The space velocity is the velocity of a star, with respect to the local
standard of rest, expressed as components along three axes. The components
are usually given as *U* (radially outward from the galactic center), *V* (in the direction of galactic rotation), and *W* (in the direction
of the galactic north pole, i.e. perpendicular to the galactic plane), with
positive signs if as indicated or negative signs if oppositely directed.
The resultant space velocity is given by the Pythagoras theorem as √(*U*^{ 2} + *V*^{ 2} + *W*^{ 2}). In the case of
the Sun, *U* = –9 km/s, *V* = +12 km/s, and *W* = +7 km/s,
giving a space velocity of 17 km/s.