beecee Posted July 7, 2021 Posted July 7, 2021 https://phys.org/news/2021-07-massive-explosion-mystery-star.html New type of massive explosion explains mystery star: A massive explosion from a previously unknown source—10 times more energetic than a supernova—could be the answer to a 13-billion-year-old Milky Way mystery. Astronomers led by David Yong, Gary Da Costa and Chiaki Kobayashi from Australia's ARC Centre of Excellence in All Sky Astrophysics in 3 Dimensions (ASTRO 3D) based at the Australian National University (ANU) have potentially discovered the first evidence of the destruction of a collapsed rapidly spinning star—a phenomenon they describe as a "magneto-rotational hypernova". The previously unknown type of cataclysm—which occurred barely a billion years after the Big Bang—is the most likely explanation for the presence of unusually high amounts of some elements detected in another extremely ancient and "primitive" Milky Way star. That star, known as SMSS J200322.54-114203.3, contains larger amounts of metal elements, including zinc, uranium, europium and possibly gold, than others of the same age. Neutron star mergers—the accepted sources of the material needed to forge them—are not enough to explain their presence. more at link................ the paper: https://www.nature.com/articles/s41586-021-03611-2 r-Process elements from magnetorotational hypernovae: Abstract: Neutron-star mergers were recently confirmed as sites of rapid-neutron-capture (r-process) nucleosynthesis1,2,3. However, in Galactic chemical evolution models, neutron-star mergers alone cannot reproduce the observed element abundance patterns of extremely metal-poor stars, which indicates the existence of other sites of r-process nucleosynthesis4,5,6. These sites may be investigated by studying the element abundance patterns of chemically primitive stars in the halo of the Milky Way, because these objects retain the nucleosynthetic signatures of the earliest generation of stars7,8,9,10,11,12,13. Here we report the element abundance pattern of the extremely metal-poor star SMSS J200322.54−114203.3. We observe a large enhancement in r-process elements, with very low overall metallicity. The element abundance pattern is well matched by the yields of a single 25-solar-mass magnetorotational hypernova. Such a hypernova could produce not only the r-process elements, but also light elements during stellar evolution, and iron-peak elements during explosive nuclear burning. Hypernovae are often associated with long-duration γ-ray bursts in the nearby Universe8. This connection indicates that similar explosions of fast-spinning strongly magnetized stars occurred during the earliest epochs of star formation in our Galaxy.
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