A source of cosmic rays radiating energies 100 times greater than those achieved at the largest terrestrial particle accelerator — the Large Hadron Collider at the European Organisation for Nuclear Research (CERN) — has been found in the innermost region of our Milky Way galaxy.
The source was revealed after a detailed analysis of the data collected by the H.E.S.S. observatory in Namibia, which was published in the latest issue of the journal Nature.
H.E.S.S. observatory is being run by an international collaboration of 42 institutions in 12 countries and has been mapping the centre of our galaxy in very high energy gamma rays for over the past 10 years.
“Somewhere within the central 33 light years of the Milky Way there is an astrophysical source capable of accelerating protons to energies of about one petaelectronvolt, continuously for at least 1,000 years,” said Emmanuel Moulin from the Saclay Nuclear Research Centre in France.
Cosmic rays with energies up to approximately 100 teraelectronvolts (TeV)1 are produced in our galaxy by objects such as supernova remnants and pulsar wind nebulae.
Theoretical arguments and direct measurements of cosmic rays reaching the Earth indicate, however, that the cosmic-ray factories in our galaxy should be able to provide particles up to one petaelectronvolt (PeV)2 at least.
While many multi-TeV accelerators have been discovered in recent years, the search for the sources of the highest energy Galactic cosmic rays has been unsuccessful.
The electrically-charged cosmic rays are strongly deflected by the interstellar magnetic fields that pervade our galaxy. Their path through the cosmos is randomised by these deflections, making it impossible to directly identify the astrophysical sources responsible for their production.
Thus, for more than a century, the origin of the cosmic rays has remained one of the most enduring mysteries of science.
In analogy to the “Tevatron” — the first human-built accelerator that reached energies of 1 TeV — this new class of cosmic accelerator has been dubbed a “Pevatron.”