Astronomers using the James Webb Space Telescope have produced the first three-dimensional map of an exoplanet’s atmosphere, revealing extreme temperature swings across the atmosphere of WASP-18b. The result marks a step beyond previous one-dimensional or two-dimensional characterizations and provides a new view of atmospheric structure on a planet orbiting another star.
The map was created from observations taken with the James Webb Space Telescope, a space observatory designed to study the Universe in infrared wavelengths. Those observations allowed researchers to probe the thermal structure of WASP-18b’s atmosphere with sufficient spatial and spectral detail to reconstruct variations in temperature at different locations and altitudes. Because the map captures temperature differences across the planet as well as vertically, it is described as three-dimensional in contrast to earlier measurements that mainly yielded average temperatures or simple day–night contrasts.
WASP-18b is an exoplanet, meaning it orbits a star beyond the Sun. The new 3D atmospheric reconstruction shows that temperatures on the planet vary dramatically, an outcome described by the research team as extreme temperature swings. Such swings indicate that temperatures differ substantially from one region of the atmosphere to another; the measurements reveal both horizontal contrasts across the planet’s face and vertical differences through layers of the atmosphere. The data therefore provide direct evidence of pronounced thermal heterogeneity in this alien world’s atmosphere.
The ability to produce a three-dimensional map represents a significant advance in observational exoplanet science because it enables study of atmospheric phenomena that cannot be captured in simpler measurements. Temperature gradients drive winds and circulation patterns, and vertical temperature structure affects where chemical species condense or are transported. By mapping temperature in three dimensions, astronomers gain a more complete view of atmospheric dynamics and energy transport on an exoplanet, and can better test models that aim to explain how heat from the host star is absorbed, redistributed and emitted.
This achievement builds on Webb’s capability to collect high-precision infrared spectra and time-resolved measurements as planets move through their orbits and present different hemispheres to the telescope. Combining those data in a way that resolves spatial and vertical variations is what made the 3D reconstruction possible. The result demonstrates that the observatory can go beyond detecting the presence of molecules or measuring bulk temperatures and can instead resolve detailed atmospheric structure on distant worlds.
With the first 3D atmospheric map in hand, researchers now have a new benchmark against which to compare theoretical models of exoplanet climates and circulation. The map’s revelation of extreme temperature swings will prompt closer examination of mechanisms that control heat redistribution and of how atmospheric chemistry responds to steep thermal gradients. The approach used on WASP-18b can also be applied to other exoplanets accessible to Webb, enabling comparative studies that may reveal how atmospheric dynamics vary with planetary properties such as mass, composition and incident stellar radiation.
As the James Webb Space Telescope continues to observe exoplanets, similar three-dimensional studies are likely to expand the range of atmospheres that can be characterized in detail. Those efforts will refine understanding of how atmospheres behave under conditions very different from those in the Solar System and will inform the development of more comprehensive models of planetary climates beyond our own.