Transit of Venus

Over the last few months it is likely that you will have heard something about the ‘transit of Venus’, an unusual celestial event in which Venus passes directly between the Earth and the Sun.

The upcoming transit will be occurring over 5 and 6 June (depending on where you are in the world) with the silhouette of Venus appearing as the planet passes in front of the sun. The next transit is not set to occur for another 105.5 years, so it really will be the last chance in your lifetime to witness it.

Due to the relationship between the orbits of Earth and Venus the transits occur in pairs, with each event separated by a period of eight years. These pairs are subsequently separated by large gaps of time (121.5 and 105.5 years), so the next pair of transits won’t be occurring until December 2117 and December 2125.

We recently featured a video from Andrew Steele which sets out the differences in these orbits and why they give rise to the unusual intervals between the transits:

Apart from being a beautiful spectacle in the sky, these events have also played an important part in gathering information about the nature of our solar system, both recently and in the past. For example, observations made by Jeremiah Horrocks (the first person to observe and record a transit) in 1639 allowed him to make an informed guess as to the distance between the Earth and the Sun (his estimate was much lower than it actually is, but he was closer than anyone else at the time). These events therefore provided astronomers with powerful observations that allowed them to define characteristics of Venus as well as the size of our Solar System.

The video below from transitofvenus.org details the scientific significance of previous transits and how scientists will be taking advantage of the upcoming event to make new observations in space:

Today, scientsits use similar techniques in the search for distant extrasolar planets or 'exoplanets'. Through the analysis of transit events across distant stars, it is possible for scientists to detect and define characteristics of far away planets using the Kepler space observatory. In particular it is the drop in a stars brightness that scientists are searching for as a planet moves in front of the star it's orbiting.

The upcoming event will actually provide scientists with a unique opportunity to test and refine their methods in their search for exoplanets. During next week's transit, scientists will take measurements of Venus using the same methods they would in the search for distant plants, they will then compare these findings with known values of Venus.This will allow scientists to get a better idea of the accuracy of their observations made on distant transit events. 

This ‘transit’ method for searching for distant exoplanets is outlined in the videos below:

With all this in mind, there’s a good incentive to try and catch the transit of Venus it in this lifetime – but before you do, make sure you check out this handy guide to find out how to view it safely (remember – never look at the sun directly!). To keep abreast of the latest transit news, Guardian Science are also providing a crowd-sourced resource pulling together transit information from around the web.

[Update 07/06/12]

NASA has released this beautiful high definition footage of the 2012 transit, captured from it's Solar Dynamics Observatory: