Wild exoplanet rains 'liquid gems' and has 'metal clouds'

The exoplanet is named WASP-121b and is the focus of a new study published in the journal Nature Astronomy.

WASP-121b is a type of gas giant exoplanet known as a "hot Jupiter" and is almost double the size of Jupiter. It was found in 2015, orbiting a star about 850 light-years from Earth. The planet is "tidally-locked" to its host star, resulting in a "day" side that permanently faces it and a "night" side that always faces away.

Astronomers from the Massachusetts Institute of Technology (MIT) have observed the perpetually dark side of the exoplanet with the most clarity yet, which, combined with their observations of the permanent dayside, have allowed them to study the atmosphere as a whole.

"Hot Jupiters are famous for having very bright day sides, but the night side is a different beast. WASP-121b's night side is about 10 times fainter than its day side," says Tansu Daylan, a TESS postdoc at MIT who co-authored the study.

Water on the dayside of the planet is exposed to temperatures over 3,000 Kelvin, ripping the molecules apart into their constituent atoms, which are then carried around to the planet's night side by winds up to 5 kilometers a second (more than 11,000 miles per hour) where they freeze before making their way back to the dayside and repeating the cycle.

The night side is cold enough that clouds of iron and corundum (a mineral that makes up rubies and sapphires) can form, which may also be carried by the extreme winds back around to the dayside. On the dayside, these metal clouds can be vaporized by the high temperatures, creating a rain of liquid gems from the corundum clouds.

You can read more from the study here.