Early in the morning of 8 June, 2004, a tiny sliver of a disc began to eat away at the sun. Over the next six hours or so, a perfect black circle – the planet Venus – emerged and slowly made its way across the face of the giant orange disc. Such ‘transits of Venus’ are even rarer than eclipses – after the next one in 2012 there won’t be another until 2117 – but the first we heard about it wasn’t from a science magazine but thanks to Wolfgang Tillmans, who photographed the cosmic alignment.

The cult German-born London-based artist has long been fascinated by astronomy and, as part of a retrospective at Serpentine Gallery, will be talking with Harvard professor and planet hunter Dimitar Sasselov this Friday as part of a special night of astronomy. Along with stars, planets and transits, the two will discuss unanswered questions about light, the beginning of infinity, the edge of visibility and our perception of colour. Dazed caught up with Professor Sasselov as he arrived in London to ask him about the Harvard Origins of Life Initiative he heads and his search for exoplanets orbiting distant suns.

Dazed Digital: How are transits of Venus (like the one Wolfgang photographed in 2004) useful in modern astronomy?
Dimitar Sasselov: The transits of Venus were not useful in astronomy for a century or so, but became useful as a way to discover exoplanets, and the transits of Venus came back into fashion. We observe Venus as a benchmark to help us observe the atmospheres to these distant exoplanets – it is really a small technical thing though, the transits of Venus are not going to return back to their old glory. However, practical things aside, they are just awesome to watch!

DD: Can you explain briefly what the Harvard Origins of Life Initiative is all about?
Dimitar Sasselov: The Initiative is about understanding the universality of life as a chemical system. This can be done in a lab, but with input from the study of the geochemistry of exoplanets. The question we ask is – if there is life on other planets should we expect it to be based on the same molecules, i.e. be universal – or should we expect it to depend on the local conditions, i.e. on the planet’s geochemistry. So, to find out we try experiments on biomolecules starting with such geochemistry conditions.

DD: How are exoplanets related?
Dimitar Sasselov: They help us do the work of synthesizing alternative biomolecules in the lab. Instead of trying blindly all kind of chemical conditions, as has been common practice until now, we use exoplanets' geochemical conditions. We assume that if life is a common phenomenon emerging on planets then we should be using them as guides in our lab experiments.

DD: What is your favourite exoplanet in the universe?
Dimitar Sasselov: It is the first one I discovered: OGLE-TR-56b

DD: What does it feel like to discover a planet orbiting a distant star?
Dimitar Sasselov: It feels great to discover a planet, just like any discovery in science, except that it has more of the feel of exploration – you can go back and look at it. However, I can never visit.

Wolfgang Tillmans and Professor Sasselov will be in conversation this Friday as part of Serpentine Gallery’s Park Nights series. For more information, visit www.serpentinegallery.org