Solar apex
Encyclopedia
The solar apex is the direction that the Sun
travels with respect to the Local Standard of Rest
. In lay terms, it's the "target" within the Milky Way that the Sun appears to be "chasing" as it orbits the galaxy. It should not be confused with the Sun's "motion" through the Zodiac
, which is not a real 3D motion, but a 2D parallax effect due to change in our vantage point (the Earth
's revolving around the Sun).
The general direction of the solar apex is southwest of the star Vega
near the constellation of Hercules
. 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 16.5 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. 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
.
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
travels with respect to the Local Standard of Rest
Local standard of rest
In astronomy, the local standard of rest or LSR follows the mean motion of material in the Milky Way in the neighborhood of the Sun. The path of this material is not precisely circular...
. In lay terms, it's the "target" within the Milky Way that the Sun appears to be "chasing" as it orbits the galaxy. It should not be confused with the Sun's "motion" through the Zodiac
Zodiac
In astronomy, the zodiac is a circle of twelve 30° divisions of celestial longitude which are centred upon the ecliptic: the apparent path of the Sun across the celestial sphere over the course of the year...
, which is not a real 3D motion, but a 2D parallax effect due to change in our vantage point (the Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
's revolving around the Sun).
The general direction of the solar apex is southwest of the star Vega
Vega
Vega is the brightest star in the constellation Lyra, the fifth brightest star in the night sky and the second brightest star in the northern celestial hemisphere, after Arcturus...
near the constellation of Hercules
Hercules (constellation)
Hercules is a constellation named after Hercules, the Roman mythological hero adapted from the Greek hero Heracles. Hercules was one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations today...
. There are several coordinates for the solar apex. The visual coordinates (as obtained by visual observation of the apparent motion) is right ascension
Right ascension
Right ascension is the astronomical term for one of the two coordinates of a point on the celestial sphere when using the equatorial coordinate system. The other coordinate is the declination.-Explanation:...
(RA) and declination
Declination
In astronomy, declination is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle. Declination in astronomy is comparable to geographic latitude, but projected onto the celestial sphere. Declination is measured in degrees north and...
(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 16.5 km/s. This speed is not to be confused with the orbital speed
Orbital speed
The orbital speed of a body, generally a planet, a natural satellite, an artificial satellite, or a multiple star, is the speed at which it orbits around the barycenter of a system, usually around a more massive body...
of the Sun around the Galactic center
Galactic Center
The Galactic Center is the rotational center of the Milky Way galaxy. It is located at a distance of 8.33±0.35 kpc from the Earth in the direction of the constellations Sagittarius, Ophiuchus, and Scorpius where the Milky Way appears brightest...
, which is about 220 km/s and is included in the movement of the Local Standard of Rest. The sun's motion in the Milky Way
Milky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...
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
William Herschel
Sir Frederick William Herschel, KH, FRS, German: Friedrich Wilhelm Herschel was a German-born British astronomer, technical expert, and composer. Born in Hanover, Wilhelm first followed his father into the Military Band of Hanover, but emigrated to Britain at age 19...
in 1783.
The solar antapex, the direction opposite of the solar apex, is located near the star Zeta Canis Minoris
Zeta Canis Minoris
Zeta Canis Minoris is a star in the constellation Canis Minor.ζ Canis Minoris is a blue-white B-type bright giant with an apparent magnitude of +5.12. It is approximately 420 light years from Earth.- References :*...
.