A team of astronomers has successfully produced the first three-dimensional map of an exoplanet, specifically WASP-18b, thanks to the capabilities of the James Webb Space Telescope. This achievement represents a significant advancement in exoplanet exploration. The researchers employed an innovative technique known as 3D eclipse mapping, or spectroscopic eclipse mapping, allowing them to monitor minute variations in light wavelengths as WASP-18b traversed behind its host star.
These detected variations facilitated the reconstruction of temperature profiles across different latitudes, longitudes, and altitudes, thereby revealing distinct thermal zones within the planet”s atmosphere. “By mapping at a wavelength that water absorbs, you can observe the water layer in the atmosphere, while wavelengths that water does not absorb allow for deeper probing,” stated Ryan Challener, a postdoctoral associate in Cornell University”s Department of Astronomy and the lead author of the study. “Combining these observations enables us to create a 3D thermal map of the atmosphere.”
WASP-18b, located approximately 400 light-years from Earth, has a mass about ten times that of Jupiter and orbits its star in just 23 hours. Its proximity to the star results in extreme atmospheric temperatures, soaring to nearly 5,000 degrees Fahrenheit (2,760 degrees Celsius). These intense conditions made WASP-18b an ideal candidate for testing the new 3D temperature mapping methodology.
The resulting map disclosed a prominent central hotspot encircled by a cooler region on the planet”s dayside. Notably, this exoplanet has a tidally locked orbit, meaning one hemisphere is consistently oriented toward its star. The findings indicated that winds on WASP-18b do not effectively distribute heat throughout the atmosphere. Intriguingly, the hotspot exhibited lower concentrations of water vapor compared to the overall average in the atmosphere. “We believe this suggests that the extreme heat in this area is causing water to disintegrate,” Challener explained, highlighting that while this had been theoretically anticipated, it is thrilling to observe it in practice.
This pioneering 3D eclipse mapping technique promises to enhance the study of exoplanets, particularly those that cannot be observed directly due to their brilliant host stars. Challener noted, “This method enables us to image exoplanets that are otherwise obscured, paving the way for a broader understanding of these distant worlds.” As the technique is applied to additional exoplanets observed by the Webb Telescope, researchers anticipate gaining a comprehensive understanding of exoplanets in three dimensions, which is an exciting prospect for the scientific community.
The findings from this research were published in the journal Nature Astronomy on October 28, 2025.
