Iron Rain Bombards a Distant Exoplanet

The distant world of WASP-76b possesses a violent environment where one side of the planet is perpetually scorched by its star whilst the other is bombarded with iron rain.

The more exoplanets astronomers discover the more they find that the universe is filled with extraordinary and unusual worlds. A prime example would be WASP-76b, which an international team of astronomers led by researchers from the University of Geneva (UNIGE) have discovered possesses one-side that is brutally bombarded by iron-rains, whilst the other is mercilessly roasted by radiation from the planet’s star.

The giant exoplanet — part of a new category of bodies called ‘ultra-hot Jupiters’ — has a scorching hot ‘dayside’ where temperatures can reach in excess of 2,40⁰⁰C, and a ‘nightside’ which is cooler by at least 1,00⁰⁰C. This means that on the former side, metals are vapourised by the ultra-hot temperatures and then carried across the planet by powerful winds. Once reaching the cooler side, the resulting iron vapour condenses into droplets of iron which rain down onto the surface of the planet.

Geneva cartoonist Frederik Peeters takes a whimsical look at a hellish landscape. Image credit: Frederik Peeters

“These planets are so hot that we are expecting molecules to disassociate into atoms,” explains Romain Allart, PhD candidate and astronomer affiliated to UNIGE and one of the co-authors of a paper discussing the conditions on WASP-76b. “This means they are…