An exoplanet where it rains liquid iron
On the tidally locked exoplanet WASP-76b, daytime temperatures surge past 2,400 degrees Celsius—hot enough to vaporize metallic iron. Powerful atmospheric winds sweep this iron gas into the planet's cooler nightside, where temperatures drop to around 1,500 degrees Celsius. This dramatic cooling forces the metallic vapor to condense into heavy clouds, unleashing torrential downpours of liquid iron droplets across the planet's perpetual darkness.
An Ultra-Hot Giant in Pisces
Roughly 640 light-years from Earth, in the constellation Pisces, orbits one of the most chemically extreme worlds yet observed: the exoplanet WASP-76b. First identified through the Wide Angle Search for Planets survey, the planet belongs to a class of celestial bodies known as ultra-hot Jupiters. These are massive gas giants that circle extraordinarily close to their parent stars, subjected to violent stellar irradiation that inflates their envelopes and reshapes their atmospheric chemistry.
WASP-76b takes just 1.8 Earth days to complete a single trip around its host star. Because it orbits so closely, intense gravitational tidal forces have locked the planet's rotation into a synchronous rhythm with its orbit. In practical terms, WASP-76b is tidally locked: one face of the planet is permanently turned toward the searing glare of its star, while the opposite hemisphere is consigned to perpetual night.
A Dayside That Vaporizes Metal
The consequences of this permanent alignment are stark. WASP-76b's dayside receives thousands of times more radiation than Earth receives from the Sun, pushing daytime atmospheric temperatures above 2,400 degrees Celsius. At these blistering energy levels, conventional atmospheric chemistry ceases to function in familiar ways. Molecular bonds are sheared apart, breaking down chemical compounds into their constituent atomic forms.
Under such intense heat, metals that would be solid rock or liquid iron on cooler worlds turn directly into atmospheric gas. Elemental iron vaporizes, rising into the upper dayside atmosphere as an invisible, atomic gas. The hemisphere facing the star effectively functions as a massive planetary smelting furnace, holding vaporized heavy metals suspended in its blistering outer layers.