The evolution of heavy element nucleosynthesis studies

The journey towards illuminating the astrophysical origins of the heaviest elements we observe in nature has taken many exciting turns. For instance, from the times of Burbidge, Burbidge, Fowler, and Hoyle (B2FH) supernovae had been a favored site for the rapid neutron capture process (r-process). Even following SN1987A (some 30 years after B2FH), core-collapse supernovae were still thought to be the source of the heaviest elements. However, thanks to both improvements in the neutrino physics treatments as well as an increased sophistication in hydrodynamic simulations, it is now thought that such sites struggle to produce elements beyond silver, and may only be able to do so in exotic cases for example with high magnetic fields. Additionally, the light curves of supernovae like 1987A are now understood to be explained by the presence of lighter elements like Ni. Flash forward to 2017, the first ever binary neutron star merger is observed and provides a detailed light curve for the community to interpret. While a full understanding of this event is still an active area of study, it pointed towards neutron star mergers as a confirmed source of the lanthanide elements made by the r process. Although mergers have been discussed as a possible r-process site for over 40 years, efforts to refine our understanding of the nucleosynthesis in mergers have now ramped up considerably, and just like for supernovae, the story of complex neutrino interactions is important in this picture as well. In addition to the neutrinos, new theoretical treatments of the nuclear physics of exotic r-process species (e.g. beta-decays) has been more actively explored in recent years. In this talk, I will review the path that heavy element studies have taken, and stop along the road to highlight the contributions of one of my scientific heroes, Baha Balantekin.