A transit of Venus across the Sun takes place when the planet Venus passes directly between the Sun and Earth, becoming visible against the solar disk. During a transit, Venus can be seen from Earth as a small black disk moving across the face of the Sun. Transits of Venus are among the rarest of predictable astronomical phenomena. They occur in a pattern that repeats every 243 years, with pairs of transits eight years apart separated by long gaps of 121.5 years and 105.5 years.
A transit of Venus took place on 8 June 2004 (photo above) and the next will be on 6 June 2012. After 2012, the next transits of Venus will be in December 2117 and December 2125. A transit of Venus can be safely observed by taking the same precautions used when observing the partial phases of a solar eclipse.
(thanks Miss Rare)The Presurfer