Astronomers obtain the first direct evidence of hydroxyl molecules in the atmosphere of a planet beyond the Solar System. Artist’s impression of an ultra-hot Jupiter exoplanet, WASP-33b. Image credit Astrobiology Center An international collaboration of astronomers led by a researcher from the Astrobiology Center and Queen’s University Belfast, and including researchers from Trinity College Dublin, has 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. This planet is an “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 (hot enough to melt most metals).