JWST Unveils First 3D Atmospheric Map of Scorching Exoplanet WASP-18b

Astronomers have achieved a groundbreaking feat by creating the first-ever three-dimensional atmospheric map of an exoplanet, WASP-18b, using the James Webb Space Telescope (JWST). This monumental achievement, detailed in a study published in Nature Astronomy on October 28, 2025, marks a significant leap in understanding distant worlds.

The target of this pioneering study, WASP-18b, is an immense "ultra-hot Jupiter" located approximately 400 light-years from Earth. This gas giant is roughly ten times the mass of Jupiter and completes an orbit around its host star in a mere 23 hours.

The newly constructed 3D map revealed astonishing temperature contrasts across WASP-18b's atmosphere. Researchers observed regions so intensely hot that they actively destroy water molecules, providing unprecedented insights into extreme planetary conditions, as reported by ZME Science on October 31, 2025.

This detailed atmospheric portrait was made possible by a novel technique called 3D eclipse mapping, also known as spectroscopic eclipse mapping. This method leverages JWST's highly sensitive instruments to track subtle changes in light as the exoplanet passes behind its star, according to the University of Maryland on November 2, 2025.

The ability to map an exoplanet's atmosphere in three dimensions offers astronomers a new lens through which to study atmospheric circulation, chemical composition, and energy distribution on alien worlds. This level of detail was previously unattainable, as noted by the Cornell Chronicle on October 28, 2025.

The research was co-led by Ryan Challener, a postdoctoral associate at Cornell University, and Megan Weiner Mansfield, an assistant professor of astronomy at the University of Maryland. Their team's findings were published in the prestigious journal Nature Astronomy, as confirmed by sci.news on October 28, 2025.

Dr. Anjali Piette from the University of Birmingham, a co-author, expressed excitement, stating that spectroscopic mapping provides a new window into the 3D structures of exoplanets, which are typically too close to their bright host stars to image directly, according to the University of Birmingham on October 28, 2025.

• WASP-18b is classified as an "ultra-hot Jupiter," a category of gas giants characterized by their extreme proximity to their parent stars. Discovered in 2009, this exoplanet is about 10 times more massive than Jupiter and orbits its star in less than an Earth day, leading to its tidally locked state where one side perpetually faces its star.

• The 3D atmospheric map was created using a sophisticated technique called spectroscopic eclipse mapping. This involves observing minute changes in light across various wavelengths as WASP-18b moves behind its star. By analyzing how different wavelengths are absorbed or emitted, scientists can reconstruct temperature and chemical profiles across the planet's latitude, longitude, and altitude.

• Key findings from the map include the identification of a blazing central hotspot on WASP-18b's dayside, surrounded by a comparatively cooler ring. Temperatures in the hotspot can reach nearly 5,000 degrees Fahrenheit (2,760 degrees Celsius). This stark contrast indicates that the planet's powerful winds are insufficient to evenly distribute heat across its atmosphere, as reported by NewsBytes on October 30, 2025.

• A significant discovery is the evidence of water molecules breaking down in the hottest regions of WASP-18b's atmosphere. Ryan Challener noted that lower water vapor levels in the hotspot suggest the extreme heat is tearing water apart, a phenomenon predicted by theory but now observed directly, according to space Daily on October 28, 2025.

• This advancement represents a crucial step in exoplanet research, moving beyond previous 2D models. The ability to visualize exoplanet atmospheres in three dimensions allows for a more comprehensive understanding of their complex weather patterns and atmospheric dynamics, similar to how Earth-based telescopes once mapped Jupiter's Great Red Spot.

• The success of this 3D mapping technique with WASP-18b opens new avenues for future studies. Researchers anticipate applying this method to a broader population of "hot Jupiters" and potentially even smaller, rocky exoplanets, enabling comparative planetology on an unprecedented scale, as stated by the Cornell Chronicle on October 28, 2025.

• Detecting exoplanets and their atmospheres is inherently challenging due to the overwhelming brightness of their host stars. The JWST's extraordinary sensitivity and its Near-Infrared Imager and Slitless Spectrograph (NIRISS) instrument were critical in overcoming these obstacles, allowing astronomers to discern the faint planetary signals, as highlighted by the University of Michigan News on October 28, 2025.