A transit of Mercury across the Sun as seen from Venus takes place when the planet Mercury passes directly between the Sun and Venus, obscuring a small part of the Sun's disc for an observer on Venus. During a transit, Mercury can be seen from Venus as a small black disc moving across the face of the Sun.
Transits of Mercury from Venus occur in an irregular fashion: sometimes there are several per decade, while on other occasions there are longer gaps. The overall frequency seems to be somewhat greater than the frequency of transits of Mercury from Earth.
Naturally, no one has ever seen a transit of Mercury from Venus.
The Mercury-Venus synodic period is 144.5662 days. It can be calculated using the formula 1/(1/P-1/Q), where P is the orbital period of Mercury (87.968435 days) and Q is the orbital period of Venus (224.695434 days).
The inclination of Mercury's orbit with respect to Venus's ecliptic is 4.33°, which is less than its value of 7.00° with respect to Earth's ecliptic.
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. [16] (http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?1894MNRAS..54..172M)
External links
JPL Solar System Simulator (http://space.jpl.nasa.gov/)
During the transit, the silhouette of Mercury was visible by day as the innermost planet passed directly between the earth and the sun.
Transit of Mercury details from Fred Espenak include a table giving the times of major events during the 2006 transit; a map showing the global visibility; and the Index to Local Circumstances, showing when the transit is seen from locations around the world.
Doppelmayer illustrates the path of Mercury across the face of the sun for the November 6, 1720, transit of Mercury.
A transit is similar to a solar eclipse by the Moon, but, although the diameter of Venus is almost 4 times that of the Moon, Venus appears much smaller because it is much further away from the Earth.
Transits of Venus are rare and currently occur in a pattern that repeats every 243 years, with pairs of transits 8 years apart separated by long gaps of 121.5 years and 105.5 years.
Horrocks corrected Kepler's calculation for the orbit of Venus and realised that transits of Venus would occur in pairs 8 years apart, and so predicted the transit in 1639, although he was uncertain of the exact time.
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