Researchers at the European Southern Observatory (ESO) have observed a super-heated exoplanet where they suspect it rains liquid iron.

With the use of the Very Large Telescope (VLT) at the ESO, a group of researchers have been studying an exoplanet orbiting a star designated WASP-76. The dayside of the planet is believed to experience super-heated temperatures of more than 2,400 degrees Celsius.

In this extreme heat, metals like iron simply evaporate into the atmosphere. Iron vapour is then carried in vigorous winds to the cooler night side where it is believed to solidify raining down on the planet’s surface.







Although not directly observed, researchers postulated the existence of the iron rain phenomenon by observing the planet’s distinct day-night atmospheric chemistry. Using the VLT’s ESPRESSO (Echelle SPectrograph for Rocky Exoplanet and Stable Spectroscopic Observations) instrument, the researchers noted a strong signature of iron vapour at the evening border that separates the day side from the night. On the morning border, however, no iron vapour was detected, suggesting that it dissipates when it enters the night side.

“The observations show that iron vapour is abundant in the atmosphere of the hot day side of WASP-76b,” explained María Rosa Zapatero Osorio, the chair of the ESPRESSO science team. “A fraction of this iron is injected into the night side owing to the planet’s rotation and atmospheric winds. There, the iron encounters much cooler environments, condenses and rains down.”

WASP-76b is located 640 light-years away in the constellation of Pisces. The observations from the planet were the first collected by the VLT’s ESPRESSO instrument back in September 2018.