On a planet some 640 light- years outside our solar system, the forecast is scorching, with a chance of liquid iron rain, new research suggests. Planets discovered outside our solar system are called exoplanets, and WASP-76b is one of the most extreme in terms of climate and chemistry. Winds on WASP-76b blow gaseous iron into cooler regions, where it condenses and falls to the planet's surface as liquid.