The passage of Venus in front of the sun is among the rarest of astronomical events, rarer even than the return of Halley's Comet every 76 years. Only six transits of Venus are known to have been observed by humans before: in 1639, 1761, 1769, 1874, 1882 and, most recently, in 2004.
The next one will occur in the year 2117. When Venus is in transit across the solar disk, the planet appears as a distinct, albeit tiny, round black spot with a diameter just 1/32nd of the sun. This size is large enough to readily perceive with the naked eye. HOWEVER ... prospective observers are warned to take special precautions (as with a solar eclipse) when attempting to view the silhouette of Venus against the blindingly brilliant solar disc.
The beginning of the transit will be visible from all of North America, Greenland, extreme northern and western portions of South America, Hawaii, northern and eastern portions of Asia including Japan, New Guinea, northern and eastern portions of Australia, and New Zealand. The end will be visible over Alaska, all of Asia and Indonesia, Australia, Eastern Europe, the eastern third of Africa, and the island nation of Madagascar.
