Webb Detects 280-Kelvin Cloud Divide on WASP-94A b, Revealing Mineral Cycle
Updated
Updated · spacedaily.com · Aug 12
Webb Detects 280-Kelvin Cloud Divide on WASP-94A b, Revealing Mineral Cycle
3 articles · Updated · spacedaily.com · Aug 12
Summary
A 6-sigma asymmetry in one Webb transit showed WASP-94A b’s cooler morning limb is cloud-covered while its hotter evening limb is clearer and shows strong water-vapour absorption.
Using NIRISS, astronomers split the transit into spectra from the planet’s leading and trailing edges instead of averaging the whole atmospheric ring into one profile.
Models indicate clouds condense near 1 millibar, rise to about 0.01 millibar, then evaporate after winds carry them into an evening limb at least 280 kelvin hotter.
An 11-sigma cloudy morning signal and 10-sigma water detection on the clear side suggest rock-forming mineral clouds are the best explanation, though the composition is modelled rather than directly sampled.
The result also revises the hot Jupiter’s inferred chemistry to roughly five times Jupiter’s heavy-element abundance and highlights how 1D atmosphere models can misread tidally locked exoplanets.