James Webb Telescope Discovers Metal Rains on Exoplanet WASP-121b

Scientists from the German Astronomical Institute used the James Webb Space Telescope to study the atmosphere of exoplanet WASP-121b. It turns out that on this distant gas giant, liquid metal, rubies and sapphires rain on the night side, and winds blow at speeds up to 18,000 kilometres per hour. The results were published in the journal Nature Astronomy.

Scientists from the German Astronomical Institute have used the James Webb Space Telescope to gain an unprecedented view of the atmosphere of exoplanet WASP-121b, and the picture is extremely dramatic. On the planet, winds blow at speeds up to 18,000 kilometres per hour and on the night side it rains liquid iron instead of water, as well as rubies and sapphires.

Rugby ball, not a round planet

The telescope observed starlight passing through the planet's atmosphere as WASP-121b moved in front of its host star. Analysis showed that this gas giant is anything but ordinary: one year there lasts only 30.5 hours, and the immense gravity of its host star has stretched the planet from a round shape into an oval resembling a rugby ball.

Behind the extremes of the weather lies the planet's so-called tidal locking with its star. WASP-121b is naturally locked, which means one side is constantly facing the star while the other side is in eternal darkness.

The evening is warmer than the morning

Researchers found that the planet's evening-side atmosphere absorbs more starlight than the morning-side atmosphere. The reason is that the evening side is significantly warmer, which causes gases to expand, so the churned-up atmosphere covers a larger area of space and blocks more light. The heat is so extreme that it can break the bonds of water molecules in the upper layers of the atmosphere.

On the cooler morning side, the situation is different: the sky there can be covered with clouds made of silicates, the constituents of rocks.

Metal rain and precious stones in the sky

On the dayside, minerals and metals evaporate vigorously, and powerful winds carry these vapours along with heat towards the night side. Upon reaching the cooler region, these substances condense and fall as precipitation, thus creating liquid iron rain and a shower of crystals resembling sapphires and rubies.

The research results have been published in the international scientific journal Nature Astronomy.