The last chance most of us will ever have to see the planet Venus pass in front of the sun is coming up this Tuesday (June 5).
On that day, more than half the world will get to see an exceedingly rare event: a transit of Venus crossing the face of the sun at inferior conjunction. A transit of Venus 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.
World visibility of the transit of Venus on 5-6 June 2012. Spitsbergen is an Artic island – part of the Svalbard archipelago in Norway – and one of the few places in Europe from which the entire transit is visible. For most of Europe, only the end of the transit event will be visible during sunrise on 6 June.
When Venus is in transit across the solar disk, the planet appears as a distinct, albeit tiny, round black spot with a diameter just 1/32 that of the sun. This size is large enough to readily perceive with the naked eye; however, prospective observers are warned to take safety precautions (as with a solar eclipse) in attempting to view the silhouette of Venus against the blindingly brilliant face of the sun. Special glasses or telescope filters must be used at all times.
Prior to local sunset, observers who are located over much of North America and the northwestern part of South America will be able to observe at least the opening stages of this most unusual celestial phenomenon.
This rare event won’t occur again until December, 2117! It’s supposed to be cloudy and rainy all day where I live, so I probably won’t get a glimpse of this phenomenon.