2025-08-31T04:52:30Z

Have you ever wondered what the building blocks of a planet might look like? Well, hold onto your telescope because a groundbreaking study led by Jenny Frediani at Stockholm University has unveiled a planet-forming disk with an astonishingly high amount of carbon dioxide!

This revelation, made possible through the powerful lens of the James Webb Space Telescope (JWST), is turning long-held beliefs about how planets form upside down. Traditionally, water vapor has been the star player in the chemistry of these cosmic nurseries, but in this mysterious disk, CO2 is stealing the spotlight. The findings are detailed in a study published in Astronomy & Astrophysics.

“Unlike most nearby planet-forming disks, where water vapor dominates the inner regions, this disk is surprisingly rich in carbon dioxide,” explains PhD student Frediani. “In fact, water is so scarce in this system that it's barely detectable—a dramatic contrast to what we typically observe.”

When a new star forms, it is usually wrapped in a gas cloud that creates a surrounding disk where new planets can be born. In traditional models of planet formation, water-rich pebbles are expected to drift from the cold outer regions of this disk toward the warmer center, where they sublimate into water vapor, creating clear signatures of H2O. But in this peculiar case, the JWST's MIRI spectrum captured a strikingly strong signature of carbon dioxide instead.

“This challenges current models of disk chemistry and evolution since the high carbon dioxide levels relative to water cannot be easily explained by standard disk evolution processes,” Frediani adds, showcasing the revolutionary nature of this discovery.

Arjan Bik, another researcher from the astronomy department, emphasized the surprise: “Such a high abundance of carbon dioxide in the planet-forming zone is unexpected. It points to the possibility that intense ultraviolet radiation—either from the host star or neighboring massive stars—is reshaping the chemistry of the disk.”

Moreover, the researchers noted rare isotopic variants of carbon dioxide, enriched in carbon-13 and specific oxygen isotopes. This finding could provide crucial insights into the mysteries surrounding the isotopic fingerprints we find in meteorites and comets—echoes of our Solar System's own formation.

Located about 53 quadrillion kilometers away in the massive star-forming region NGC 6357, this CO2-rich disk was discovered by the eXtreme Ultraviolet Environments (XUE) collaboration. Their focus is on how intense radiation affects disk chemistry. Maria-Claudia Ramirez-Tannus, the lead of the XUE team, couldn't hide her excitement: “It reveals how extreme radiation environments—common in massive star-forming regions—can alter the building blocks of planets. Since most stars and likely most planets form in such regions, understanding these effects is essential for grasping the diversity of planetary atmospheres and their habitability potential.”

Thanks to the JWST's MIRI instrument, astronomers can now examine distant, dust-enshrouded disks in incredible detail at infrared wavelengths. This capability is shedding light on the physical and chemical conditions that drive planet formation. By contrasting these vibrant environments with quieter areas, researchers are piecing together the complex puzzle of how planetary systems emerge.

With the MIRI instrument jointly developed by astronomers from Stockholm University and Chalmers, the future of exoplanet exploration looks bright. The study titled “XUE: The CO2-rich terrestrial planet-forming region of an externally irradiated Herbig disk” not only challenges our understanding but also opens up new avenues for research into planetary habitability and atmospheric diversity.