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Ecliptic longitude Ecliptic longitude or celestial longitude (symbols: heliocentric l, geocentric λ) measures the angular distance of an object along the ecliptic from the primary direction. Like right ascension in the equatorial coordinate system, the primary direction (0° ecliptic longitude) points from the Earth towards the Sun at the ...
Solar longitude, commonly abbreviated as Ls, is the ecliptic longitude of the Sun, i.e. the position of the Sun on the celestial sphere along the ecliptic.It is also an effective measure of the position of the Earth (or any other Sun-orbiting body) in its orbit around the Sun, [1] usually taken as zero at the moment of the vernal equinox. [2]
The ecliptic or ecliptic plane is the orbital plane of Earth around the Sun. [ 1 ] [ 2 ] [ a ] It was a central concept in a number of ancient sciences, providing the framework for key measurements in astronomy, astrology and calendar-making.
The heliocentric ecliptic system describes the planets' orbital movement around the Sun, and centers on the barycenter of the Solar System (i.e. very close to the center of the Sun). The system is primarily used for computing the positions of planets and other Solar System bodies, as well as defining their orbital elements .
The ecliptic longitudes are given in terms of a zodiac sign and a number of degrees and fractions of a degree. The zodiac signs each represent exactly 30°, starting with Aries representing longitude 0° to 30°. The degrees are added to the lower limit of the 30-degree range to obtain the longitude.
In celestial mechanics, true longitude is the ecliptic longitude at which an orbiting body could actually be found if its inclination were zero. Together with the inclination and the ascending node, the true longitude can tell us the precise direction from the central object at which the body would be located at a particular time.
From the above definitions, define the longitude of the pericenter. ϖ = Ω + ω. Then mean longitude is also [1] L = ϖ + M. Another form often seen is the mean longitude at epoch, ε. This is simply the mean longitude at a reference time t 0, known as the epoch. Mean longitude can then be expressed, [2] L = ε + n(t − t 0), or
In describing the Keplerian elements of an orbit, ☊ is sometimes used to denote the ecliptic longitude of the ascending node, although it is more common to use Ω (capital omega, and inverted ℧), which were originally typographical substitutes for the astronomical symbols. [110] The symbols for aspects first appear in Byzantine codices. [3]