Astronomers have achieved a significant milestone by creating the first three-dimensional map of an exoplanet, specifically WASP-18b. Utilizing the advanced capabilities of the James Webb Space Telescope, researchers employed a novel technique known as 3D eclipse mapping to analyze the planet’s atmospheric conditions. This groundbreaking work represents a pivotal advance in exoplanet research.
With WASP-18b located approximately 400 light-years from Earth, the planet is about ten times the mass of Jupiter and completes its orbit around its star in just 23 hours. Its proximity to the host star results in extreme atmospheric temperatures, reaching nearly 5,000 degrees Fahrenheit (2,760 degrees Celsius). These intense conditions made it an ideal candidate for testing the new mapping technique.
Researchers tracked subtle changes in various light wavelengths as WASP-18b transited behind its star. This allowed them to reconstruct temperature variations across different latitudes and altitudes within the planet’s atmosphere. Ryan Challener, a postdoctoral associate at Cornell University and lead author of the study, explained the process: “If you build a map at a wavelength that water absorbs, you’ll see the water deck in the atmosphere, whereas a wavelength that water does not absorb will probe deeper. If you put those together, you can get a 3D map of the temperatures in this atmosphere.”
The resulting map revealed distinct temperature zones, including a bright central hotspot surrounded by a cooler ring on the dayside of the planet. This uneven distribution of heat is attributed to the planet’s tidally locked orbit, where one side consistently faces its star. Notably, the hotspot displayed lower water vapor levels than the overall atmospheric average. Challener emphasized the significance of this finding, stating, “We think that’s evidence that the planet is so hot in this region that it’s starting to break down the water.”
The implications of this research extend beyond WASP-18b. The new 3D eclipse mapping technique is poised to revolutionize exoplanet observations. Challener noted that it opens opportunities to study exoplanets that are otherwise obscured by the brightness of their host stars. As this technique is applied to additional exoplanets observed by the James Webb Space Telescope, scientists anticipate a deeper understanding of exoplanets as a diverse population.
The team’s findings were published in the journal Nature Astronomy on October 28, 2025, marking a new chapter in the exploration of distant worlds. The research not only enhances our knowledge of WASP-18b but also sets the stage for future investigations into the atmospheric dynamics of exoplanets across the galaxy.