On January 3, 2025, an international team of scientists announced significant findings from the James Webb Space Telescope (JWST) that may resolve long-standing questions regarding planet formation in the early universe. The research focused on the star cluster NGC 346 in the Small Magellanic Cloud, a galaxy known for its low abundance of heavy elements.
Previously, the Hubble Space Telescope had observed a massive planet orbiting a star formed just one billion years after the Big Bang. This discovery raised questions, as early stars, composed primarily of hydrogen and helium, were thought to lack the necessary heavy elements for planet formation.
JWST observations revealed that protoplanetary disks around stars in NGC 346 have lifetimes exceeding those seen around younger stars in the Milky Way, challenging existing models of planet formation. Typically, these disks dissipate within 2-3 million years, yet many young stars in NGC 346, estimated to be 20-30 million years old, still possess these disks.
The findings suggest that the mechanisms governing protoplanetary disk longevity may differ in environments with fewer heavy elements. Researchers propose two potential explanations: one involves the reduced effectiveness of radiation pressure in dispersing disks lacking heavier elements, while the other posits that larger gas clouds may lead to more massive disks that take longer to dissipate.
These insights not only shed light on the conditions of early star formation but also prompt a reevaluation of established theories regarding the architecture of planetary systems. The JWST continues to reveal unexpected complexities of the universe, encouraging astronomers to reconsider long-held beliefs.