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In astronomy, a syzygy (from the Ancient Greek ''suzugos'' (σύζυγος) meaning, "yoked together") is a straight-line configuration of three celestial bodies in a gravitational system.〔 〕 The word is often used in reference to the Sun, Earth, and either the Moon or a planet, where the latter is in conjunction or opposition. Solar and lunar eclipses occur at times of syzygy, as do transits and occultations. The term is often applied when the Sun and Moon are in conjunction (new moon) or opposition (full moon). The word ''syzygy'' is often loosely used to describe interesting configurations of planets in general. For example, one such case occurred on March 21, 1894 around 23:00 GMT, when Mercury transited the Sun (as could have been seen from Venus), and Mercury and Venus both simultaneously transited the Sun as seen from Saturn. It is also used to describe situations when all the planets are on the same side of the Sun although they are not necessarily in a straight line, such as on March 10, 1982. On June 3, 2014, the ''Curiosity'' rover observed the planet Mercury transiting the Sun (from Mars), marking the first time a planetary transit has been observed from a celestial body besides Earth.〔 == Occultations, transits, and eclipses == Syzygy sometimes results in a transit, an occultation or an eclipse. * An occultation occurs when an apparently larger body passes in front of an apparently smaller one. * A transit occurs when a smaller body passes in front of a larger one. * * In the combined case where the smaller body regularly transits the larger, an occultation is also termed a secondary eclipse. * An eclipse occurs when a body disappears or partially disappears from view, either by an occultation, as with a solar eclipse, or by passing into the shadow of another body, as with a lunar eclipse (thus both are listed on (NASA's eclipse page )). Transits and occultations of the Sun by Earth's Moon are called solar eclipses regardless of whether the Sun is completely or partially covered. By extension, transits of the Sun by a satellite of a planet may also be called eclipses, as with the transits of Phobos and Deimos shown on (NASA's JPL photojournal ), as may the passage of a satellite into the planet's shadow, as with this (eclipse of Phobos ). The term ''eclipse'' is also used more generally for bodies passing in front of one another. For example, (a NASA Astronomy Picture of the Day ) refers to the Moon eclipsing and occulting Saturn interchangeably. 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「Syzygy (astronomy)」の詳細全文を読む スポンサード リンク
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