Astronomical conjunction

In astronomy, a conjunction occurs when two astronomical objects or spacecraft have either the same right ascension or the same ecliptic longitude, usually as observed from Earth. The astronomical symbol for conjunction is ☌ (in Unicode U+260C) and handwritten . The conjunction symbol is not used in modern astronomy. It continues to be used in astrology.

When two objects always appear close to the ecliptic – such as two planets, the Moon and a planet, or the Sun and a planet – this fact implies an apparent close approach between the objects as seen on the sky. A related word, appulse, is the minimum apparent separation on the sky of two astronomical objects.

Conjunctions involve either two objects in the Solar System or one object in the Solar System and a more distant object, such as a star. A conjunction is an apparent phenomenon caused by the observer's perspective: the two objects involved are not actually close to one another in space. Conjunctions between two bright objects close to the ecliptic, such as two bright planets, can be seen with the naked eye.

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