A research team led by ICREA researcher Mark Gieles at the University of Barcelona has developed a model explaining how extremely massive stars, with masses exceeding 1,000 times the Sun, dictated the formation and chemical evolution of the universe's oldest star clusters by Robert Schreiber
Berlin, Germany (SPX) Nov 05, 2025
A research team led by ICREA researcher Mark Gieles at the University of Barcelona has developed a model explaining how extremely massive stars, with masses exceeding 1,000 times the Sun, dictated the formation and chemical evolution of the universe's oldest star clusters.
The model adapts the inertial-inflow framework to early-universe conditions, demonstrating that turbulent gas in primordial clusters enabled the creation of stars up to 10,000 solar masses. These massive stars generated powerful winds enriched with products of high-temperature hydrogen fusion, mixing with untouched cluster gas to form new, chemically distinct stars.
The study, published in Monthly Notices of the Royal Astronomical Society, clarifies long-standing mysteries in the chemical composition of globular clusters, including their characteristic enrichment in helium, nitrogen, oxygen, sodium, magnesium, and aluminium. Researchers found that a small number of massive stars could imprint lasting chemical signatures across entire clusters, linking formation physics with observed chemical features.
Laura Ramirez Galeano and Corinne Charbonnel from the University of Geneva emphasized that while nuclear processes in the cores of such stars matched abundance patterns, the new model provides a natural route for forming these stellar giants within dense clusters.
Formation and enrichment occurred over the initial one-to-two million years-preceding any supernova activity-so cluster gas avoided supernova contamination.
The discovery also offers a new perspective on galaxies observed by the James Webb Space Telescope; nitrogen-rich galaxies likely host clusters dominated by extremely massive stars formed during early galaxy assembly.
Paolo Padoan, from Dartmouth College and ICCUB-IEEC, underscored the critical role of such stars in first-galaxy formation, explaining both high luminosity and nitrogen enrichment seen in JWST protogalaxies.
The team concluded these giant stars likely ended as intermediate-mass black holes, over 100 solar masses, possibly detectable via gravitational wave signals.
The model unifies star formation physics, cluster evolution, and chemical enrichment, demonstrating that extremely massive stars were central to early galaxy formation and the emergence of the first black holes.
Research Report:Globular cluster formation from inertial inflows: accreting extremely massive stars as the origin of abundance anomalies
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