Atmosphere on ‘super Earth’ analysed for first time

Scientists have established the composition of the atmosphere of a "super-Earth" planet in orbit around a distant star. This is the first time such an analysis has been achieved on what is known as an exoplanet – a planet outside the Solar System.

There is plenty of hydrogen, that could serve as fuel, and all the helium you might want for inflating balloons. However, you would not want to live there. The atmosphere of planet 55 Cancrie e is laced with prussic acid – hydrogen cyanide.

Light rays coming through the atmosphere allow scientists to read its spectral lines which reveal which chemicals are present. However, it is a huge challenge to examine these rays given the much brighter light streaming from 55 Cancri e’s star.

A research team involving University College London and KU Leuven in Belgium found a way around this using new processing methods on data supplied by the Nasa/Esa Hubble Space Telescope.

“This is a very exciting result because it’s the first time that we have been able to find the spectral fingerprints that show the gases present in the atmosphere of a super-Earth [an exoplanet with a mass between one and 10 times that of Earth],” explains Angelos Tsiaras, a PhD student at UCL, who developed the analysis technique along with his colleagues Ingo Waldmann and Marco Rocchetto.

Little similarity

The results of the research reveal an inhospitable planet overall. It is rocky but there is little similarity with Earth beyond this.

Its diameter is twice that of our planet but it has eight times the mass of Earth so people would barely be able to stand or breathe because of the much stronger gravitational pull.

Planet 55 Cancri e is about 40 light years away and whizzes around its sun to complete a full "year" in just 18 hours. A sun umbrella would not help at all given surface temperatures are about 2,000 degrees, the researchers say.

The spectral data shows it is a very lightweight atmosphere consisting mostly of hydrogen and helium and without any water vapour. The signature for hydrogen cyanide is there too and this generally indicates a carbon-rich atmosphere. However, findings linked to carbon have yet to emerge from the data analysis.

Details of their work were published on Tuesday in the Astrophysical Journal.