Astronomy Colloquium

For decades,  supernova remnants have been considered as the principal contributors to the galactic cosmic rays up to the so-called knee around 1 PeV (10^{^15} eV).   However, the recent observations and theoretical studies raised doubts inside the CR community regarding the ability of SNRs to operate as PeVatrons.  Supernova remnants remain major cosmic ray factories in the Milky Way, but presumably with a reduced role at highest energies.  On the other hand,  multi-TeV gamma-ray observations provide evidence that the clusters of young massive stars do host proton PeVatrons.  In the context of the origin of highest energy galactic cosmic rays, the role of the supermassive black hole in the galactic center could be significant as well.