The exoplanet that rains molten iron

Spotted in 2013 and further investigated by the Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO) instrument on the Very Large Telescope in 2020, WASP-76b is a planet that’s tidally locked to its parent star BD+01 316. This means that one side of the planet permanently faces the star, causing scorchingly hot temperatures of around 2,500 degrees Celsius (4,532 degrees Fahrenheit) – hot enough to vaporise iron.

The star-facing side of WASP-76b is roasted by radiation that is thousands of times more intense than Earth receives from the Sun, while the side that faces away from the F-type star experiences perpetual night. Yet even though the ‘dayside’ of the planet experiences hellish temperatures, that doesn’t mean that conditions on the ‘nightside’ are a walk in the park. The side of WASP-76b that faces away from the star is cooler by at least 1,000 degrees Celsius (1,832 degrees Fahrenheit), but this means that when iron vapour is carried across to the other side by powerful winds it cools, forming liquid droplets. These droplets of molten iron then fall, bombarding the cooler side of the planet.