Venus Transit (Eurovenus episode #5)
May 09th, 2016
On the 6 June 2012, Venus passed directly in front of the Sun (as viewed from Earth). This transit of Venus is a very rare event, occurring roughly twice per century. The transit of Venus is of historical importance - because the transits of 1761 and 1769 were used to determine the Earth-Sun distnace, which is the "astronomical unit" by which all distances in the Universe were measured. After the astronomical unit had been determined, it had seemed that the transit of Venus might be merely an astronomical curiosity.

But planetary transits have now gained a newfound importance: they are the principal tool used to study the atmospheres of planets orbiting other stars (exoplanets). Planetary transits are being used to search for water, ozone and other chemical species which can indicate how Earthlike other worlds may be.

In this context, the transit of Venus takes on a newfound importance: We can study the atmosphere of Venus using the transit methods which we use to study exoplanets - and then check our answers, because we have a spacecraft at Venus so know its atmospheric state.

In this film we follow Paolo Tanga, from the Observatory of the Cote d'Azur, who developed a set of coronagraphs for the study of light refracted through the atmosphere of Venus. These were then deployed to many sites around the world, to ensure that at least some of them had good weather; the same techniques were also used to analyse data from space-based solar observatories.

We are pleased to release this film on this day, on which a transit of Mercury is occurring - an event only slightly less rare than the transit of Venus...