Astronomers have detected helium gas in the atmosphere of a planet that orbits a star far beyond our solar system for the first time. An international team, led by Jessica Spake from the University of Exeter in the UK, discovered evidence of the inert gas on ‘super-Neptune’ exoplanet WASP-107b, 200 light years from Earth and in the constellation of Virgo. The breakthrough, made from observations using the Hubble Space Telescope, revealed an abundance of helium in the upper atmosphere of the exoplanet, which was only discovered in 2017, according to the study published in the journal Nature. “The helium we detected extends far out to space as a tenuous cloud surrounding the planet,” said Tom Evans from the University of Exeter. “If smaller, Earth-sized planets have similar helium clouds, this new technique offers an exciting means to study their upper atmospheres in the very near future,” Evans said.
The strength of the helium signal detected was so large that scientists believe the planet’s upper atmosphere extends tens of thousands of kilometres into space. Helium is the second most common element in the universe and it has long-since been predicted to be one of the most readily-detectable gases on giant exoplanets. However, this is the first time that the gas has been successfully found, researchers said. The team believes that the study could pave the way for scientists to discover more atmospheres around Earth-sized exoplanets across the galaxy. WASP-107b is a very low-density planet similar in size to Jupiter, but with only 12 per cent of its mass. Orbiting its host star every six days, it has one of the coolest atmospheres of any of the exoplanets discovered, although at 500 digress Celsius is still radically hotter that Earth, according to the researchers.
By analysing the spectrum of light passing through the upper part of the exoplanet’s atmosphere, the researchers were able to detect the presence of helium in an excited state. The significant strength of the signal measured exploited a new technique that does not rely on ultraviolet measurements which have historically been used to study upper exoplanet atmospheres. The team believes this new technique, which uses infrared light, could open up new paths to exploring the atmospheres of more Earth-sized exoplanets found in the further reaches of the universe.