“`html

An innovative method is assisting researchers in comprehending the atmospheres of celestial bodies beyond our solar system—many of which are unlike those orbiting our star

A global consortium of astronomers, including Emily Rauscher from the University of Michigan, has produced the initial 3D representation of a celestial body revolving around another star. This illustration uncovers an atmosphere featuring varying temperature regions—one so extreme that it disintegrates water vapor.

“Partially, this outcome is incredibly fascinating because it showcases a novel approach,” stated Rauscher, an associate professor of astronomy at U-M. “From a scientific perspective, this result is equally captivating since, for this specific exoplanet, temperatures rise to astonishing levels.”

The group, co-directed by Ryan Challener of Cornell University and Megan Weiner Mansfield from the University of Maryland, shared their results in the journal Nature Astronomy.

The team’s thermal map details a planet recognized as WASP-18b, a gas giant resembling Jupiter within our solar system, yet it resides 400 light-years away from Earth. It orbits remarkably close to its star, being sufficiently hot that researchers classify it as an “ultra-hot Jupiter.”

This endeavor exemplifies a method known as 3D eclipse mapping, or spectroscopic eclipse mapping. It builds upon a 2D framework previously published by the same team in 2023, which highlighted eclipse mapping’s capacity to utilize the highly sensitive observations of the JWST, Earth’s premier space telescope. Managed by NASA, the JWST also receives support from the European Space Agency and the Canadian Space Agency.

“Eclipse mapping enables us to visualize exoplanets that remain unseen directly, owing to their host stars’ excessive brightness,” remarked Challener, a postdoctoral associate at Cornell. “With this telescope and this innovative technique, we can begin to comprehend exoplanets in ways similar to our solar system companions.”

Much like earlier Earth-based telescopes allowed astronomers to start detailing Jupiter’s Great Red Spot, JWST now empowers scientists to characterize a greater number of exoplanet atmospheres using this method, the team noted.

Challener previously served as a postdoctoral researcher in Rauscher’s group at U-M, where he initiated the development of computer coding capable of extracting 3D thermal data from JWST’s information. Mansfield also possesses a U-M association: Elements of the approach she contributed to the new project were initiated at a workshop led by Rauscher in 2018.

“I certainly feel a sense of pride in that,” Rauscher remarked. “Here at Michigan, we’ve played a role in facilitating this observation.”

The coalition composed of approximately three dozen researchers from over 20 global institutions. The investigation was funded by JWST’s Transiting Exoplanet Community Early Release Science Program.

Mapping Distant Cosmos

Identification of exoplanets poses a challenge right from the start. Light emitted by their host stars can overshadow what the planets emit. In terms of luminosity, exoplanets usually possess less than 0.1% of their stars’ brightness.

“The analogy is akin to a firefly before a lighthouse,” Rauscher commented. “However, we know when the planet is positioned in front of and behind the star. We are actually capable of measuring that minute dip that represents the light from the planet.”

JWST can accurately assess how that light diminishes as the planet travels behind the star. This facility allows scientists to associate slight variations in luminosity with specific areas to create a brightness representation across a range of different light wavelengths, or colors. That spectroscopic data can be translated into temperatures across three dimensions: latitude, longitude, and altitude.

WASP-18b, approximately ten times the mass of Jupiter, completes its orbit in merely 23 hours and reaches temperatures nearing 5,000 degrees Fahrenheit. This provided JWST with a comparatively robust signal, making it an excellent test subject for the new mapping method.

The fresh perspective of the exoplanet confirmed distinct spectroscopic regions in WASP-18b’s visible “dayside,” which consistently faces the star due to its tidally locked orbit. The planet exhibits a circular “hotspot” where the most direct starlight strikes, and where atmospheric winds appear too feeble to redistribute the heat. Encircling the hotspot is a cooler ring closer to the planet’s observable edges, or limbs. Notably, Challener noted that measurements indicated lower concentrations of water vapor in the hotspot compared to WASP-18b’s overall average.

“We believe that this is indicative that the planet’s temperature in this area is so elevated that it’s beginning to decompose the water,” Challener explained. “This had been postulated by theory, but it’s genuinely thrilling to visualize this through actual observations.”

Further JWST observations could enhance the spatial resolution of the initial 3D eclipse map, the team stated. Moreover, this technique can already assist in mapping the 3D temperature variations of other hot Jupiters, which comprise hundreds of the more than 6,000 confirmed exoplanets to date.

“One of the truly fascinating aspects of exoplanets is that the majority we have discovered are entirely dissimilar from the ones in our solar system,” Rauscher remarked. “Thus, it’s immensely enjoyable to explore how we can apply what we understand, more or less, about our solar system to these unusually different scenarios.”

“`