Ultra-hot Jupiters are half boiling hellscape, half cloudy oasis. Molecules in the atmosphere on the planets’ day sides may be broken into their atomic building blocks by the blistering heat, only to recombine into clouds that rain down liquid iron on the cooler night sides.

The hottest planets in the universe are gas giants a bit larger than Jupiter that orbit close to their stars. For worlds this close in, one side is always facing the star, …