Disks that form planets last longer in the early universe, according to the Webb Telescope

The NASA/ESA/CSA James Webb Space Telescope has resolved a long-standing mystery about planet formation during the universe’s early stages. As detailed in The Astrophysical Journal, recent discoveries reveal that planet-forming disks around stars persisted much longer than previously believed, even in environments with scarce heavy elements.

In 2003, the NASA/ESA Hubble Space Telescope made a groundbreaking observation, identifying massive planets orbiting ancient stars that lacked heavy elements like carbon and iron—key ingredients traditionally thought essential for planet formation. This unexpected finding left scientists questioning how such planets could form and grow under these seemingly inhospitable conditions.

To delve deeper, the Webb Telescope directed its attention to NGC 346, a large star cluster in the Small Magellanic Cloud, one of the Milky Way’s closest neighbors. This region is particularly significant because its chemical makeup, dominated by hydrogen and helium, mirrors the elemental composition of the early universe. The cluster’s stars, aged between 20 and 30 million years, were found to host planet-forming disks that remained intact far longer than similar structures within the Milky Way.

According to Guido De Marchi of the European Space Research and Technology Centre (ESTEC), these disks are not only still present around these stars but are also actively accumulating material, defying existing models. Conventional theories suggest that planet-forming disks should dissipate within a few million years, particularly in low-metal environments. However, Webb’s observations have upended this notion, showing that disks in such conditions can survive and evolve over much longer timescales. Co-investigator Elena Sabbi of NOIRLab’s Gemini Observatory noted that prior models did not account for the possibility of such disks persisting in metal-poor environments.

Scientists propose two possible reasons for this extended disk lifespan. One explanation is that radiation pressure, which usually disperses these disks, is less effective in environments lacking heavy elements. Another theory posits that stars in such conditions originate from larger gas clouds, resulting in bigger disks that take significantly longer to dissipate.

These findings offer fresh perspectives on planetary evolution in the universe’s infancy, suggesting that planets could have formed and grown even in scenarios once deemed unfavorable. With Webb’s advanced capabilities, astronomers now possess concrete evidence that challenges and reshapes traditional theories about how planets emerge and develop.