dr hab. Tobias Fischer, UWr

The origin of heavy elements in the universe

The production of elements heavier than iron in the universe poses sever challenges to the current understanding of explosive cosmic events. In particular during the early evolution of our galaxy, when the metal content known as metallicity was generally low, the explosions of massive stars was the major site, if not the only one. Even though the heaviest elements, e.g., Gold, Lead and even the actinide elements such as Uranium and Plutonium are robustly produced in the violent event of two merging neutron stars, they can have no contribution to the chemical enrichment of the galaxy at vanishing metallicity. It leaves the explosions of massive stars as only site, for which I will review in this talk our current picture of the associated synthesis of heavy elements, which canonically yields the production of elements with atomic numbers only up to 32<Z<50 such as Zirconium and Strontium. It emphasizes the puzzle of the observed enrichment of metal-poor stars with significantly heavier elements, while simultaneously pointing to a few rare events associated with massive star explosions that enriched the galaxy with these elements at low metallicity. Still today, their origin and nature is yet to be discovered.