This video shows a temperature forecast spanning 130 days on the exoplanet WASP-121 b. The brighter the colour, the hotter that patch of planet, with the hottest locations shown in yellow/white and the coolest in dark red/black.

WASP 121-b is tidally locked, meaning that the same side of the planet is always facing its host star –we call this the ‘day side’. The brighter yellow regions indicate areas on the day side of the exoplanet where the temperature soars well above 2000 K because it orbits extremely close to its host star (just 2.6% of the Earth-Sun distance!).

Astronomers suspect that the high temperatures cause iron and other heavy metals to evaporate into higher layers of the atmosphere on the day side of WASP-121 b, before cooling and partially falling back down onto lower layers on the dark side, meaning that it rains iron. Some of the heavy metals also escape into space from the upper atmosphere.

In this research, an international team of astronomers assembled and reprocessed Hubble observations of WASP-121 b made in the years 2016, 2018 and 2019. This provided them with a unique dataset that allowed them not only to analyse the atmosphere of WASP-121 b, but also to see how it changed across several years. The team then used sophisticated modelling techniques to demonstrate that the changes they saw over time could be explained by weather patterns in the exoplanet's atmosphere, as seen here.

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