Conjunction

Conjunction is a phenomenon in which two or more celestial bodies have equal geocentric celestial longitudes (see Celestial longitudes) or right ascensions The conjunction of an outer planet with the Sun: the geocentric celestial longitudes of the planet and the Sun are equal. The conjunction of Mercury and Venus with the Sun: the geocentric celestial longitudes of the planet and the Sun are equal; the conjunction is called superior or inferior depending on whether the Sun is between the Earth and the planet or the planet is between the Earth and the Sun. The conjunction of two planets, of a planet with the Moon or with a star: the right ascensions of the two bodies are equal.