Enhanced production of 60 Fe in massive stars.

Massive stars are a major source of chemical elements in the cosmos, ejecting freshly produced nuclei through winds and core-collapse supernova explosions into the interstellar medium. Among the material ejected, long-lived radioisotopes, such as ⁶⁰ Fe (iron) and ²⁶ Al (aluminum), offer unique signs of active nucleosynthesis in our galaxy. There is a long-standing discrepancy between the observed ⁶⁰ Fe/ ²⁶ Al ratio by γ-ray telescopes and predictions from supernova models. This discrepancy has been attributed to uncertainties in the nuclear reaction networks producing ⁶⁰ Fe, and one reaction in particular, the neutron-capture on ⁵⁹ Fe. Here we present experimental results that provide a strong constraint on this reaction. We use these results to show that the production of ⁶⁰ Fe in massive stars is higher than previously thought, further increasing the discrepancy between observed and predicted ⁶⁰ Fe/ ²⁶ Al ratios. The persisting discrepancy can therefore not be attributed to nuclear uncertainties, and points to issues in massive-star models.
(© 2024. The Author(s).)