The James Webb Space Telescope (JWST) has revealed that planets can form in some of the Milky Way’s harshest environments, challenging previous assumptions about planet formation. Observations of the XUE 1 protoplanetary disk, located in a radiation-intense star-forming region, show it can withstand extreme ultraviolet radiation while containing traces of water—a key ingredient for Earth-like planets. The disk is compact with truncated edges due to the intense UV radiation affecting its gas chemistry and temperature. Despite these conditions, the presence of water and other planet-building materials suggests that habitable worlds could emerge even in such hostile settings. These findings, published in The Astrophysical Journal on May 20, 2025, expand our understanding of where and how planets can form.
Here are some key findings:
- Planet Formation in Extreme UV Environments: JWST observations have shown that protoplanetary disks – the swirling rings of gas and dust where planets are born – can survive and evolve even in regions with intense ultraviolet (UV) radiation from massive stars.
Previously, it was thought that such harsh conditions would hinder planet formation. Notably, the inner regions of these disks, where rocky planets are expected to form, appear to be shielded from the most damaging UV radiation. The presence of water, a crucial ingredient for Earth-like planets, has also been detected in these hostile environments. - Long-lasting Planet-forming Disks in Metal-poor Environments: JWST has found that planet-forming disks can persist much longer than previously thought, even in environments with a low concentration of heavy elements, similar to the early universe.
This challenges traditional models that suggested planets couldn't form in such conditions due to the rapid dissipation of these disks. This extended lifespan provides more time for planets to grow, even large ones like Jupiter. - Direct Imaging of Infant Planets in Different Stages: JWST has directly imaged young, gas giant planets in different stages of their infancy around a sun-like star.
One planet was observed with a dusty circumplanetary disk (where moons might form), while another had an atmosphere brimming with silicate clouds. This illustrates the complex and varied nature of planetary system development, with planets in the same system appearing to be at different stages of formation. - Unusual Planetary System Architectures: JWST has also observed exoplanets with highly unusual orbits, such as the frigid gas giant 14 Herculis c, which orbits its star in a violently tilted "X"-shaped formation with another planet.
This suggests that some planetary systems experienced more chaotic early evolution, potentially involving the ejection of other planets.
These discoveries are revolutionizing our understanding of planet formation, suggesting that the conditions for habitable worlds might be much broader and more resilient than previously imagined. JWST's unique sensitivity in infrared wavelengths allows astronomers to peer into these hidden processes and is continuously challenging existing models of exoplanet atmospheres and formation.