Nuclear cluster configurations at the threshold and the onset of the formation of elements in primordial stars

The colloquium will address some aspects of the first step in the formation of heavier elements in our universe. The first stars emerged about 400 Million years after the Big Bang burning entirely on primordial nuclear fuel through the pp-chains. The lack of Carbon in the stellar abundance distribution prohibits a stabilization of these stars predicted to have masses between 5 and 150M. The star contracts under his own gravitational weight, gradually increasing the internal temperature and density conditions. New nuclear reaction patterns emerge converting the initial hydrogen and helium fuel into carbon, nitrogen, and oxygen (CNO). These reaction patterns rely on nuclear cluster resonances in light nuclei causing a significant enhancement of reaction rates and may even trigger the first neutron-induced reaction sequences leading to the formation of heavier elements beyond the CNO range. Such patterns have not yet been considered for stellar environments, but may alter our current interpretation of nucleosynthesis in the first generation of stars as first simulations demonstrate.

About the Speaker:

Michael Wiescher is the Freimann Professor for Physics at the University of Notre Dame. He primarily works in the field of Nuclear Astrophysics but has also build an experimental program in the analysis of cultural heritage objects at the Nuclear Science Laboratory (NSL) at Notre Dame.

Wiescher has served as director of the NSL from 2005 to 2020; he was the founding director of the Joint Institute for Nuclear Astrophysics (JINA) from 2003 to 2015 and still served on its executive committee. He is presently the director of the Notre Dame Institute for Structure and Nuclear Astrophysics. He also holds appointments as Adjunct Professor at Michigan State University, as Visiting Professor at Surrey University, UK and as Heraeus Visiting Professor at the University of Frankfurt, Germany.

Wiescher has more than 435 scientific publications and books, on different aspects of quiescent and explosive nucleosynthesis in stars. He served on more than 100 advisory and organization committees of national and international conferences. He also contributed to numerous reports and panel meetings towards the long-range science planning in the United States. Wiescher was elected to Fellow of the American Physical Society in 1998, received the Hans Bethe Prize of the DNP & DAP in 2003, and a Humboldt-Forschungspreis, AvH Foundation, Germany in 2007. In 2010 he was elected as Fellow of the American Assoc. for the Advancement of Science, and in 2017 he received the Heraeus Visiting Professor Award, University of Frankfurt. In the same year, he became an Elected Scientific Member of the Academiae Europaeae. In 2018 he received the Laboratory Astrophysics Prize 2018, LAD Division of the American Astronomical Society.