Cosmic rays can mean any high energy from the cosmos and were only referred to as rays for historical reasons – in that they thought cosmic rays were electromagnetic radiation. However generally cosmic rays refer to high energy particles with mass whereas high energy in the form of gamma rays and/or X-rays are photons. These cosmic particles were discovered in 1912 by Victor Hess when he ascended to 5300 meters above sea level in a hot air balloon and detected significantly increased levels of ionization in the atmosphere.
Ultra-High Energy Cosmic Rays (UHECRs) are extremely energetic sub-atomic particles with energies of the order 100 PeV (that is 100,000 trillion electron volts). Their origin has long remained a mystery. However, an intriguing coincidence in the energy generation rates of UHECRs, cosmic neutrinos and gamma rays are comparable – indicating a unified picture.
Fang and Murase report in a recent paper that powerful black hole jets could be the key. They suggest that the black hole jets accelerate charged particles to extreme energies. The most energetic of the cosmic rays escape the jet and escape the magnetized environment of the galaxy cluster. It is these particles that contribute to the UHECRs. However, some of the particles that are energetic enough to escape the jet are not energetic enough to escape the magnetic pull of the cluster. These particles interact with the magnetized environment producing cosmic neutrinos and gamma rays with energies of PeV (1000 trillion electron volts) and TeV (a trillion electron volts), respectively. Fang and Murase ran computer simulations of this model and found it matched up perfectly with observations.
The implications of any model that supports a unified picture and agrees with observations is huge and now any future observations of these particles will have a whole new meaning.