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JWST Delivers First 3D Map of an Exoplanet's Atmosphere

A spectroscopic eclipse‑mapping analysis of WASP‑18b reveals a dayside hotspot with signs of water breakdown.

Overview

  • A Nature Astronomy paper published October 28 details the first validated three‑dimensional temperature map of an exoplanet, with an accompanying arXiv preprint.
  • The team reanalyzed multi‑wavelength JWST NIRISS data to perform spectroscopic eclipse mapping, resolving atmospheric structure in latitude, longitude, and altitude.
  • The dayside shows a concentrated hotspot at the substellar point and a cooler ring near the limbs, indicating limited heat redistribution by winds.
  • Spectra indicate lower water vapor in the hottest region than the planet’s average, consistent with thermal dissociation of water molecules.
  • The mapping reveals weaker longitudinal temperature gradients than some models predicted and establishes a technique that can be refined with further JWST observations and applied to many hot Jupiters.