'5,545 light years away': NASA's James Webb Telescope detects CO2-rich planet-forming disk challenging models of planet birth

A team led by Jenny Frediani at Stockholm University has identified a planet-forming disk with an unexpectedly high concentration of carbon dioxide (CO2), challenging existing theories of how planets are assembled. The findings, made with the James Webb Space Telescope (JWST), were published in Astronomy & Astrophysics.

The observations reveal that, unlike most nearby planet-forming disks where water vapour dominates the inner zones, this system is unusually rich in CO2. Frediani, a doctoral student in the Department of Astronomy at Stockholm University, explained that water in this disk is so scarce that it is barely detectable, representing a significant contrast to the norm.

In typical models, newly formed stars generate a surrounding disk from which planets eventually take shape. Pebbles covered in water ice drift inward from colder outer regions, and the increase in temperature causes the ice to sublimate, usually producing strong water vapour signatures in the inner disk. In this case, however, JWST’s MIRI instrument recorded a stronger CO2 signal instead.

“This result cannot be accounted for by conventional disk evolution processes,” said Frediani. Arjan Bik, researcher at Stockholm University, added that the unusually high abundance of CO2 may point to the influence of strong ultraviolet radiation, either from the host star or from nearby massive stars, reshaping the chemical environment.

The team also observed isotopic variants of CO2, enriched in carbon-13 and in oxygen isotopes 17O and 18O. These isotopologues, clearly identifiable in JWST data, may provide clues to longstanding questions about the isotopic fingerprints found in meteorites and comets, remnants of the early solar system.

The disk was detected in NGC 6357, a massive star-forming region located around 5,542 light-years away from Earth. The work forms part of the eXtreme Ultraviolet Environments (XUE) collaboration, which examines how strong radiation fields influence disk chemistry. According to Maria-Claudia Ramirez-Tannus of the Max Planck Institute for Astronomy, who leads the XUE project, understanding such processes is central to explaining the diversity of planetary systems and their potential habitability.

JWST’s MIRI instrument, partly developed with contributions from Stockholm University and Chalmers, enables astronomers to observe such distant dust-shrouded disks in infrared wavelengths, providing valuable data on conditions that govern planet formation.