The origin of cosmic rays

The search for the origin of cosmic rays is a quest of almost a hundred years. A recent theoretical proposal gives quantitative predictions, which can be tested with data. Specifically, it has been suggested, that all cosmic rays can be attributed to just three source sites: i) supernova explosions into the interstellar medium, ii) supernova explosions into a stellar wind, and iii) powerful radiogalaxies. The cosmic rays from any extragalactic source suffer from interaction with the microwave background, leading to the Greisen-Zatsepin-Kuzmin cutoff. While the particle energies, the spectrum and the chemical composition of cosmic rays over the energy range from about GeV to about 100 EeV can be interpreted in the theory, there are exciting measurements now: New measurements show that there are cosmic ray events beyond the Greisen-Zatsepin-Kuzmin cutoff. We discuss here possible sources, and specifically ask whether powerful radiogalaxies are suitable candidates. The basic concepts used here are the minimal hypothesis that the intergalactic magnetic field is given by the galaxy distribution, and the observation that radio galaxies also cluster like galaxies.Comment: Lecture at the meeting Trends in Astroparticle Physics, Stockholm September 1994, 8 pages, uuencode