The William Herschel Telescope, located on La Palma in the Canary Islands, was used for the UK astronomers' research. Credit: Nik Szymanek


Astronomers from the UK’s Open University, University of Warwick and University of Sheffield are hoping that a new technique they have pioneered may help shed new light on the chemical and geological composition of rocky exoplanets.

The team have been using the William Herschel Telescope (WHT) in La Palma, Spain to study a small, rocky exoplanet lying 1,500 lightyears from Earth called KIC 1255b.

KIC 1255b is unusual because its orbit brings it so close to its parent star that the intense heat of its sun’s light is vapourising the very rock of which the planet is composed.

As a result, were you close enough to see KIC 1255b it would look more like a comet than a planet, with a long tail of dust trailing behind it in its orbit.

It’s this tail that the UK team have been looking at, using a ‘visitor instrument’ on the WHT called ULTRACAM.

It blocks around 1 per cent of its star’s light each time it transits it – that’s about the same as the percentage of the Sun’s light that would be blocked by a transit of Jupiter as seen from KIC 1255b’s location, and vastly greater than the proportion of light that's blocked by tiny Mercury-sized KIC 1255b itself.

The amount of light blocked gives astronomers a clear indication of the tail’s size, which varies over time, while by studying how light from the star is scattered by the dust in the tail – which can be achieved by taking simultaneous, multi-colour measurements with ULTRACAM – the team hope to soon deduce the chemical composition of the dust – and hence of the exoplanet itself.

Jakob Bochinski, an Open University research student who is lead author of a report on the team’s findings published in The Astrophysical Journal, said:

“This is an incredibly exciting breakthrough as it opens up the possibility of determining the chemical composition of this rocky planet.


By doing that we can find out how typical our Solar System is, helping us learn more about how Earth and other planets were formed."