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A transit of Mercury across the Sun as seen from Saturn takes place when the planet Mercury passes directly between the Sun and Saturn, obscuring a small part of the Sun's disc for an observer on Saturn. During a transit, Mercury can be seen from Saturn as a small black disc moving across the face of the Sun. Naturally, no one has ever seen a transit of Mercury from Saturn, since nobody has ever been to Saturn. Nor is one likely to be seen in the foreseeable future. However, and unobserved one happened on September 27, 2012. It is possible that a transit of Mercury could be observed from the surface of one of Saturn's moons rather than from Saturn itself. The times and circumstances of the transits would be slightly different. The Mercury-Saturn synodic period is about 88.694 days. This can be calculated using the formula synodic period = 1/(1/P - 1/Q), where P is the sidereal orbital period of Mercury (87.968 days) and Q is the orbital period of Saturn (10746.940 days). The inclination of Mercury's orbit with respect to Saturn's ecliptic is about 6.38 degrees, which is less than the inclination of about 7.00 degrees with respect to the ecliptic of the Earth. The transits of Mercury as seen from Saturn are found to occur in clusters, with two such clusters happening every 30 years or so. The transit that occurred on March 21, 1894 was a particularly interesting one because it happened on the same day as both transit a transit of Venus from Saturn and of a transit of Mercury from Venus. However, no two of these transits were simultaneous. Also interesting will the transit of December 9, 2056, when Mercury barely misses transiting the Sun, but Venus begins an actual transit about six hours later. Note: the image linked to in the following table does not take into account the finite speed of light. The distance of Mercury from Saturn at inferior conjunction is about 9.3 astronomical units or about 80 light-minutes. It will take about eight hours for Mercury to transit the face of the Sun, hence the image corresponds fairly closely to what would actually be seen by an observer on Saturn. ==References== * Albert Marth, ''Note on the Transit of Mercury over the Sun’s Disc, which takes place for Venus on 1894 March 21, and on the Transits of Venus and Mercury, which occur for Saturn’s System on the same day'', Monthly Notices of the Royal Astronomical Society, 54 (1894), 172–174. () 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 Mercury from Saturn」の詳細全文を読む スポンサード リンク
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