The transit of Venus in 2012
What is a transit and why is this such an unusual phenomenon?
Venus, the Earth and the Sun will be aligned 5-6 June 2012. This event is rare and is therefore much anticipated by the scientific community. The conditions for this perfect alignment of these three celestial bodies are fulfilled very rarely: this transit will be only the eighth since the invention of the telescope!
Let’s look at the dates of the transits of Venus to demonstrate the sequence. Once a Venus transit has occurred, the next will occur 8 years later, then it will be 121 years and 6 months for the next, then again 8 years, then 105 years and 6 months for the fourth passage of Venus and then the sequence restarts.
Transits therefore occur in pairs (with a spacing of 8 years) and then are separated by an interval of more than a century. The last one occurred in 2004 and the next one will occur in 2117.
An observation of the transit of Venus was the most famous measurement of the distance between the Earth and the Sun – a distance that is key to measuring all the other distances between celestial bodies, and which is itself now a unit (called astronomical unit)
In the 21st century, the study of Venus transits allows astronomers to test their equipment, considering Venus as an exoplanet. This occasion is therefore the last chance before the next Venus transit, which will only occur next century.