Astronomers have observed an ultra-hot giant planet in the constellation of Pisces where they suspect it rains iron, a finding that may lead to better ways of studying the climate of the most extreme planets outside the Solar System.
According to the researchers, including those from the University of Geneva in Switzerland, the giant exoplanet WASP-76b is at a distance that would take even light 640 years to reach the Earth, and has a day side where temperatures climb above 2400 degrees Celsius – high enough to vaporise metals.
The study noted that strong winds carry iron vapour to the cooler night side where it may be condensing into iron droplets.
The researchers said this phenomenon happens because the ‘iron rain’ planet only ever shows one face – its day side – to its parent star, while its cooler night side remains in perpetual darkness.
They explained that like the Earth’s Moon, WASP-76b is ‘tidally locked’, meaning it takes as long to rotate around its axis as it does to go around the star. According to the scientists, the day side is so hot that molecules separate into atoms, and metals like iron evaporate into the atmosphere.
This extreme temperature difference between the day and night sides results in vigorous winds that bring the iron vapour from the ultra-hot day side to the cooler night side, where temperatures decrease to around 1500 degrees Celsius.