how is heliocentric longitude is used to show the position of planets in orbit around the sun?

Answer 1

Since planets orbit the Sun, it is much simpler to specify their positions in solar (heliocentric) coordinates rather than Earth (geocentric) coordinates.

The heliocentric longitude is somewhat like right ascension. Heliocentric longitude is zero at the position of the Earth on the vernal equinox and the Earth's heliocentric longitude increases by about 1 degree per day (360 degrees per year).

Precision calculations for planetary positions are usually done in heliocentric longitude (L), elevation above or below the ecliptic (B) and distance from the Sun (R). To figure the place of a planet in the sky, the LBR coordinates of the planet and the Earth are both calculated and the difference is the vector from Earth to the planet.

Answer 2

Heliocentric Longitude