Transit of Venus
In a transit of Venus, the planet passes directly between the Sun and the Earth, appearing as a dot moving across the Sun's face. While transits are similar to a solar eclipse by the Moon, Venus casts a smaller shadow and takes several hours to cross the Sun's face.
Transits of Venus are relatively rare, occurring in June and December according to a 243-year pattern. Pairs of transits occur eight years apart, most recently in June of 2012 and 2004, December of 1874 and 1882, and June of 1769 and 1762.
Jeremiah Horrocks and William Crabtree made the first scientific observations of the December 1639 transit from separate locations in Lancashire.
James Cook's Endeavour voyage was one of five expeditions the Royal Society organised to record the 1769 transit.
The next transits will occur in December 2117 and 2125.
