Heavy Elements in a Swirling Storm: How Neutron Stars Inside Common Envelopes Forge the Universe’s Rarest Atoms

Anninos et al. model how a neutron star inside a common envelope can forge heavy elements as infalling gas heats, cools, and cycles through turbulent convection. Their simulations show that both r-process and rare p-nuclei can form, even in slightly proton-rich conditions, because high entropy and rapid expansion prevent neutrons from being fully locked into alpha particles. Some material escapes the star’s gravity, suggesting CE systems may contribute to the Universe’s heaviest elements.