Carbon dioxide, a potential fingerprint of life, has been discovered for the first time in the atmosphere of a planet orbiting another star.

However, the planet, HD 189733b, is too hot to be habitable.

But the discovery nonetheless has scientists excited, because carbon dioxide is one of four chemicals that life can generate, so being able to detect it shows that astronomers have the ability to find the signs of life on other worlds.

"This is the first detection of carbon dioxide in the atmosphere of an extrasolar planet, which means that three of the Big Four biomarkers for habitable/inhabited worlds have now been seen: water, methane, and now carbon dioxide," explained Alan Boss, a planet-formation theorist at the Carnegie Institution of Washington who was not involved in the finding. "The only one that has not yet been detected is oxygen/ozone."