local standard of rest (LSR)

A frame of reference centred on the Sun in which the average velocity of the stars in the vicinity of the Sun is zero. Each star, including the Sun, is moving relative to the LSR. The Sun's motion, at about 20 km/s, is directed towards the solar apex. The LSR's velocity of 250 km/s with respect to the centre of the Galaxy is a measure of the Galaxy's general rotation in the Sun's neighbourhood.