Solar apex

This is not to be confused with the Sun's apparent motion through all constellations of the zodiac, which is an illusion caused by the Earth's orbit.

Thus the Sun moves towards the apex (a relatively local point) at about 1⁄13 our spiral arm's orbital speed.

[4] The nature and extent of the solar motion was first demonstrated by William Herschel in 1783, who also first determined the direction for the solar apex, as Lambda Herculis, 10° away from today's accepted position.

[8] The catalog from the Hipparcos astrometric satellite and measurements with objective prisms lead to a new set of values.

The calculation of the local standard of rest itself is subject to issues due to inhomogeneous stellar velocities[10] and high sensitivity to parameters.