Astronomers have detected a new chemical signature in the atmosphere of an extrasolar planet (a planet that orbits a star other than our Sun). The hydroxyl radical (OH) was found on the dayside of the exoplanet WASP-33b — a so-called ‘ultra-hot Jupiter’, a gas-giant planet orbiting its host star much closer than Mercury orbits the Sun and therefore reaching atmospheric temperatures of more than 2,500° C.
