Scientists have reported the first conclusive discovery of water vapor in the atmosphere of an exoplanet, or a planet beyond our solar system. This artist’s impression shows an infrared view of a gas-giant exoplanet transiting across the face of its star. NASA’s Spitzer Space Telescope observed this type of system in infrared light, providing the breakthrough. The planet, HD 189733b, lies 63 light-years away in the constellation Vulpecula.