Imagine a world where winds blow at 18,000 kmph with nighttime showers of liquid metal, rubies and sapphires. Astronomers say WASP-121b is an “ultra-hot Jupiter” that ranks among the most extreme planets beyond the solar system.

The gas giant orbits its host star at such a close distance that a single “year” there lasts just 30.5 hours. Temperatures on its dayside climb high enough to vaporise metals, while iron may condense and fall as rain on the cooler nightside.