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An alignment of two bodies in the solar system with the Earth, so that they appear to be at the same place (or nearly so) in the sky as seen from the Earth. A planet is said to be at conjunction when it is at the same ecliptic longitude as (and so is approximately in line with) the Sun. The planets Mercury and Venus can form such a line by being either between the Earth and the Sun, when they are said to be at inferior conjunction, or behind the Sun as seen from Earth, an alignment called superior conjunction. The planets further from the Sun than the Earth can only come to superior conjunction. Conjunctions can also occur between planets or between the Moon and one or more planets but, in that context, the word is often used more loosely to describe an approach within a few degrees. See also: ecliptic coordinates. |