The astrophysical r-process: what we are learning from gravitational waves, dwarf galaxies, and stellar archaeology
Understanding the origin of the elements is one of the major challenges of modern astrophysics. The rapid neutron-capture process, or r-process, is one of the fundamental ways that stars produce the elements listed along the bottom two-thirds of the periodic table, but key aspects of the r-process are still poorly understood. I will describe three major advances in the last few years that have succeeded in confirming neutron star mergers as an important site of the r-process. These include the detection of freshly produced r-process material powering the kilonova associated with the merger of neutron stars detected via gravitational waves (GW170817), the detection of a dwarf galaxy where most of the stars are highly enhanced in r-process elements (Reticulum II), and advances in deriving abundances of previously-undetected r-process elements (Se, Te, Pt) in ultraviolet and optical spectra of metal-poor stars in the Milky Way halo field. I will describe future prospects that connect these three research directions and future rare isotope accelerators to associate specific physics with specific sites of the r-process. Finally, I will highlight the major impact of Jim Lawler's atomic spectroscopy group at Wisconsin in enabling these advances.