What is "solar apex"

n. (context astronomy English) The point to which the Sun appears to be moving with respect to the local stars

n. the point on the celestial sphere toward which the sun and solar system appear to be moving relative to the fixed stars [syn: apex, apex of the sun's way] [ant: antapex]

The solar apex, or the Apex of the Sun's Way, refers to the direction that the Sun travels with respect to the Local Standard of Rest. This is not to be confused with the Sun's apparent motion through the constellations of the zodiac, which is illusory – this supposed motion is actually caused by the Earth revolving around the Sun.

The solar apex is in the constellation of Hercules, southwest of the star Vega. There are several coordinates for the solar apex. The visual coordinates (as obtained by visual observation of the apparent motion) is right ascension (RA) and declination (dec) of 30° North (in galactic coordinates: 56.24° longitude, 22.54° latitude). The radioastronomical position is RA and dec (galactic coordinates: 58.87° longitude, 17.72° latitude).

The speed of the Sun towards the solar apex is about 20 km/s. This speed is not to be confused with the orbital speed of the Sun around the Galactic center, which is about 220 km/s and is included in the movement of the Local Standard of Rest. Thus the Sun gains distance towards the apex at about 1/13 its orbital speed. The sun's motion in the Milky Way is more complex than a simple orbit, it also shifts ("bobs") up and down with respect to the galactic plane.

The nature and extent of the solar motion was first demonstrated by William Herschel in 1783.

The solar antapex, the direction opposite of the solar apex, is located near the star Zeta Canis Minoris.