Colour enhanced drawing of the transit of Venus of 1761,by Nicholas Ypey. Although the coronal detail on the sun is not actually observable,the path of the transit is accurately depicted. Transits of Venus across the disk of the Sun are among the rarest of planetary alignments. Only eight such events have occurred since the invention of the telescope (1631,1639,1761,1769,1874,2004 and 2012). A transit of Venus across the Sun takes place when the planet Venus passes directly between the Sun and Earth (or another planet),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. Venus transits are historically of great scientific importance as they were used to gain the first realistic estimates of the size of the Solar System |