Transit of Venus

Update June 7th: Two additional images added to this article showing the Black Drop and a wonderful sunset view from Greece.

Well, we didn’t get an in-world venue sorted, but on the night of 5th / 6th of June 2012, a bunch of us gathered (with thousands of others) on Twitter to share in the Transit of Venus. Feeds were widely available from NASA and elsewhere, although many of us stayed with http://www.slooh.com, which provided feeds from telescopes right across the world – Norway, Sweden, mainland USA, Japan, Hawaii, the Pacific, New Zealand, Australia – ten locations in all, hoping to ensure the widest possible coverage should inclement weather interfere with things.

The transit itself has been written about rather a lot – so if you want an overview of the historical context, Wikipedia offers a very informative piece, including the sad tale of Guillaume Le Gentil, which was referred to several times in the SLOOH webcast, and which has itself been immortalised in a the play Transit of Venus. The article also touches on James Cook’s role in observing the transit of 1769.

Balu Pulipaka of Indiana captured this image of the “Black Drop” effect as Venus passes through 2nd Contact

Venus imaged by NASA’s Solar Dynamics Observatory

Today, the Transit is no longer used to help us understand the broader sweep of the solar system per se, but has, in both 2004 and 2012,  been used to assist scientists in the study of exoplanets. In this, the 2012 transit is liable to have been more valuable than 2004, due to increased solar activity as we approach a period of Solar Maximum in the Sun’s (roughly) 11-year cycle.

The view from Greece: Spyros Skikos captures a unique sunset with his camera, Venus prominent against the Sun

A pink-filtered image from the University of Oslo, showing the end of the transit, with Venus between 3rd and 4th contacts. Note the solar prominence on the limb of the sun just below it (image: http://www.slooh.com)

The 2012 event also helped with the calibration of instruments aboard NASA’s Solar Dynamics Observatory, while observations of the event taken from the Svalbard archipelago coupled with those from the European Venus Express mission in orbit around the planet will also hopefully increase our understanding of the planet’s atmosphere and climatology.

Black & white images from Broome, Australia, showing Venus (left) and sunspots on the face of the sun (image: http://www.slooh.com)

For casual observers, the four periods of contact were perhaps the most enthralling – the points where Venus first “touches” the limb of the sun, then slowly moves inside the sun’s disk until it is entirely “inside) (1st and 2nd Contact) and the point at which it touches the limb of the sun on the other side on its way “out” (3rd Contact), before vanishing entirely (4th Contact).

Of these in turn, the 2nd and 3rd contacts are of interest as they give rise to the so-called “black drop”. This is when light distortion possibly due to sunlight refracting through Venus’ atmosphere  appears to “pull” the edge of Venus to the edge of the sun, elongating it into a tear-like shape, with the limb of the sun appearing to “bend in” towards it.

I’ve compiled a modest slideshow of the event from a number of the SLOOH feeds. The first 10 are from the University of New Mexico feed, while the last ten are from Oahu and the Haleakala volcano observatory, Hawaii. You get the opportunity to see the next transit of Venus live until 2117…

(Click here to see the slideshow full screen)

NASA also offer a composite video of the event using images captured by SDO:

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