Black Hole as Extreme Particle Accelerator

Astrophysicists have theorized for decades that the mysterious, ultrahigh-energy cosmic rays (UHECRs) detected on Earth could come from active galactic nuclei (AGNs), the supermassive black holes at the centers of galaxies. The particle acceleration mechanism, however, has been unclear. Now a team of researchers has used simulations of unprecedented size to propose a mechanism. The results strengthen the idea of AGNs as UHECR sources, although some experts caution that the simulations have limitations when used to predict protons of such high energies.