UMD Astronomer Co-leads Creation of First 3D Temperature Map of Distant Exoplanet

Astronomers have generated the first three-dimensional map of a planet orbiting another star, revealing an atmosphere with distinct temperature zones—one so scorching that it breaks down water vapor, according to a new paper published Wednesday in the journal Nature Astronomy.

Co-led by the University of Maryland and Cornell University, the research details the team’s effort to create a temperature map of WASP-18b—a gas giant known as an “ultra-hot Jupiter,” located 400 light-years from Earth. The group’s map is the first to apply a technique called 3D eclipse mapping; it builds on a 2D model that members of the same team published in 2023, which demonstrated eclipse mapping’s potential to tap into highly sensitive observations by NASA’s James Webb Space Telescope (JWST).

“This technique is really the only one that can probe all three dimensions at once: latitude, longitude and altitude,” said the paper’s co-lead author, Megan Weiner Mansfield, an assistant professor of astronomy at UMD. “This gives us a higher level of detail than we’ve ever had to study these celestial bodies.”

Using this technique, the researchers say they can now begin mapping atmospheric variations for many similar types of exoplanets observable by JWST, just as Earth-based telescopes long ago observed Jupiter’s Great Red Spot and banded cloud structure.

While the team’s earlier 2D map of WASP-18b utilized a single light wavelength, or color, the new 3D map reanalyzed the same observations from JWST’s Near-Infrared Imager and Slitless Spectrograph instrument in many wavelengths. Each color on the map corresponded to different temperatures and altitudes within WASP-18b’s gaseous atmosphere, which could then be pieced together to create the new, more detailed three-dimensional map. 

The new 3D view confirmed spectroscopically distinct regions—differing in temperature and possibly in chemical composition—in WASP-18b's visible “dayside,” the side that always faces the star due to its tidally locked orbit. The planet features a circular “hot spot” where the most direct starlight lands and where winds apparently aren't strong enough to redistribute the heat. Surrounding the hot spot is a colder “ring” nearer the planet's outer visible edges, or limbs. Notably, measurements showed lower levels of water vapor in the hot spot than WASP-18b's average.

This article was adapted from text provided by Cornell University.