In the scenario Mumpower proposes, a massive star begins to die as its nuclear fuel runs out. No longer able to push up against its own gravity, a black hole forms at the star’s center. If the black hole is spinning fast enough, frame-dragging effects from the extremely strong gravity near the black hole wind up the magnetic field and launch a powerful jet. Through subsequent reactions, a broad spectrum of photons is created, some of which are at high energy.

The jet blasts through the star ahead of it, creating a hot cocoon of material around the jet, “like a freight train plowing through snow,” Mumpower said. At the interface of the jet with the stellar material, high-energy photons (that is, light) can interact with atomic nuclei, transmuting protons to neutrons.

Existing atomic nuclei may also be dissolved into individual nucleons, creating more free neutrons to power the r process. The team’s calculations suggest the interaction with light and matter can create neutrons incredibly fast, on the order of a nanosecond.

Because of their charge, protons get trapped in the jet by the strong magnetic fields. Neutrons, which are chargeless, are plowed out of the jet into the cocoon. Having experienced a relativistic shock, the neutrons are extremely dense compared with the surrounding stellar material, and thus the r process may ensue, with heavy elements and isotopes forged and then expelled out into space as the star is ripped apart.