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A transit of Venus across the Sun as seen from Saturn takes place when the planet Venus passes directly between the Sun and Saturn, obscuring a small part of the Sun's disc for an observer on Saturn. During a transit, Venus can be seen from Saturn as a small black disc moving across the face of the Sun. == Characteristics == Naturally, no human has ever seen a transit of Venus from Saturn, nor is this likely to happen in any foreseeable future. However, the 21 December 2012 transit was observed by the VIMS spectrometer aboard the ''Cassini'' spacecraft, for the purpose of testing the instrument's suitability for exoplanet studies. The instrument attempted to observe chemical signatures; no images were returned since the entire solar disk only covered a few pixels.() The next transit will take place on 14 January 2028. A transit could hypothetically be observed from the surface of one of Saturn's moons rather than from Saturn itself. The times and circumstances of the transits would naturally be slightly different. The Venus-Saturn synodic period is 229.494 days. It can be calculated using the formula 1/(1/P-1/Q), where P is the sidereal orbital period of Venus (224.695434 days) and Q is the orbital period of Saturn (10746.940 days). The inclination of Venus's orbit with respect to Saturn's ecliptic is 2.06°, which is less than its value of 3.39° with respect to Earth's ecliptic. The transit that occurred on 21 March, 1894 was particularly interesting because later on the same day there was a transit of Mercury from Saturn, followed by the beginning of a transit of Mercury as viewed from Venus, although no two of the transits occurred simultaneously. Also interesting is the event of 9 December, 2056, when a Venus transit will begin a few hours after a near-miss by Mercury. 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「Transit of Venus from Saturn」の詳細全文を読む スポンサード リンク
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