Through detailed calculations of stellar nucleosynthesis, astronomers know the mix of elements that Population III supernovae of various masses should produce. So-called Population II stars are born from interstellar clouds that are already slightly enriched with heavier elements, forged in the cores of Population III stars and blown into space when these earlier stars exploded. So, to learn more about the first generation of stars, Hartwig and his Japanese colleagues studied the composition of the second generation. Little is known about the circumstances of their origin, or their masses - information that is crucial for better understanding the formation and early evolution of the very first galaxies. Born shortly after the Big Bang from primordial clouds of hydrogen and helium, these massive stars (also called Population III stars, for historical reasons) only lived for a few million years or so before going supernova. No one has ever seen a true first-generation star. “It’s an exciting result, with far-reaching consequences,” says Simon Portegies Zwart (Leiden Observatory, The Netherlands), who wasn’t involved with the study. That’s what Tilman Hartwig (University of Tokyo) and his colleagues conclude in a recent paper in The Astrophysical Journal, after comparing observations with computer calculations. More often than not, the universe’s very first stars didn’t live a solitary life but formed in small groups and clusters instead. The central star is nearing the end of its short life, about to go supernova. This artist’s impression shows a field of Population III stars, the first stars to shine in the universe.
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