The Gran Telescopio Canarias on La Palma in the Canary Islands was used for the research. Picture credit: Pablo Bonet

Breakthrough in the study of distant planet atmospheres

A research team led by the University of Exeter has discovered a previously undetected element in the atmosphere of a planet almost 500 light years from Earth.

Using a cutting-edge technique on one of the most powerful telescopes in the world, the international team have identified potassium in the atmosphere of the planet XO-2b, located in the Lynx constellation.

This comes at the same time as another research team, led by the University of Florida, have also announced finding potassium on another distant planet - HD 80606 b, which is 190 light years from Earth.

Both the planets are known as hot-Jupiters, meaning they are similar in size to Jupiter but are much hotter because they orbit far closer to their respective stars – giving them temperatures of up to 1,000°C or more.

This extreme heat means potassium, which is locked in a solid state on Earth, should be in a gaseous form within the planet’s atmosphere. However, until now no-one has been able to detect it, though it has long been theorized to be an important part of hot-Jupiter atmospheres.

Dr David Sing, from the University of Exeter’s School of Physics and leader of the research, said: “We’ve finally found an element we’ve been long expecting, and hoping to find.  It’s a large step forward as it supports many theories about hot-Jupiter planets.

“The detection has been made using a new technique which we will be able to apply on many other planets, leading to a far broader understanding of hot-Jupiters and other kinds of planets as we compare their atmospheres.”

The find was made using a method known as narrowband transit spectrophotometry — which involves measuring light that has passed through the upper atmospheres of a planet and using highly sensitive equipment to analyse the data.

Dr Eric Ford, from the University of Florida, said: “The new technique opens the door to comparing the abundances of multiple atoms and molecules in several more planets.

“While both planets in the Florida and Exeter studies have potassium, there are interesting differences in the details that provide information about the structure of the planets’ atmospheres.”

Both studies were carried out using the Gran Telescopio Canarias, which has a huge mirror more than 10 metres wide and is located more than 7,000 ft above sea-level on a volcanic peak on La Palma in the Canary Islands.

Alongside this is the OSIRIS instrument, which precisely measures light received through the telescope within a small range of colours. This minimizes the distorting effects of the Earth’s atmosphere and allows detailed readings to be taken.

When a planet becomes backlit as it passes in front of its star, the light that has passed through its atmosphere is measured by OSIRIS. Because atoms and molecules absorb light at different wavelengths, scientists can analyse the light readings and determine which molecules are present – in this case, potassium.

Dr Sing said: “The transit technique can reveal the size of the planet, the radius, how dense it is, how massive it is, and to see what’s in its atmosphere. It’s very difficult to do because the signatures are so small that you need very precise equipment, but the technology is now there and has opened a whole new area of scientific research.

“This means we can really start to look at the diversity of exoplanets and compare them in more detail than previously. It’s possible the technique could one day be used to help in the search for life on other planets.”

The two groups’ findings are available online at the arXiv preprint server,, and have been submitted to the journals Astronomy & Astrophysics and the Monthly Notices of the Royal Astronomical Society.

Dr Sing from the University of Exeter and Knicole Colón from the University of Florida will present their findings at the ExoClimes 2010 conference to be held at the University of Exeter on 7-10 September.

Some of the world’s leading experts in Earth, Solar System and Exoplanet climatology will be attending the event to discuss recent results in this rapidly moving area of research.

The event will feature a host of talks and lectures on a range of subjects, from studying the atmospheres of hot gas giant planets to putting Earth’s climate change in context.

Anyone wanting more information about the event can go to

Date: 31 August 2010

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