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A conjunction occurs when two astronomical objects or spacecraft have either the same right ascension or the same ecliptic longitude, normally when observed from the Earth.〔 〕 In the case of two objects that always appear close to the ecliptic – such as two planets, or the Moon and a planet, or the Sun and a planet – this implies an apparent close approach between the objects as seen on the sky. In contrast, the term appulse is defined as the minimum apparent separation on the sky of two astronomical bodies.〔 〕 Conjunctions therefore involve two Solar System bodies, or one Solar System body and one more distant object such as a star. A conjunction is an apparent phenomenon caused by perspective only: there is no close physical approach in space between the two objects involved. Conjunctions between two bright objects close to the ecliptic, such as two bright planets, can be easily seen with the naked eye and can attract some public interest. The astronomical symbol of conjunction is ☌ (in Unicode U+260C) and handwritten: 20px. However, this symbol is never used in modern astronomy and is of historical interest only. ==Passing close== More generally, in the particular case of two planets, it means that they merely have the same right ascension (and hence the same hour angle). This is called conjunction in right ascension. However, there is also the term conjunction in ecliptic longitude. At such conjunction both objects have the same ecliptic longitude. Conjunction in right ascension and conjunction in ecliptic longitude do not normally take place at the same time, but in most cases nearly at the same time. However, at triple conjunctions, it is possible that a conjunction only in right ascension (or ecliptic length) occur. At the time of conjunction – it does not matter if in right ascension or in ecliptic longitude – the involved planets are close together upon the celestial sphere. In the vast majority of such cases, one of the planets will appear to pass north or south of the other. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Conjunction (astronomy)」の詳細全文を読む スポンサード リンク
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