Speeding charged particles — far more energetic than any we can create in laboratory particle accelerators — constantly bombard the Earth’s atmosphere. But what extreme environments produce these high-energy particles? A new study may have identified one cosmic accelerator in our galaxy.
Diagram showing cosmic ray flux as a function of energy. The lower-energy cosmic rays (yellow region) are thought to be produced by the Sun. Intermediate-energy cosmic rays (blue region) are likely of galactic origin, and the highest-energy cosmic rays (pink region) likely come from beyond the galaxy. [Sven Lafebre]
At any given moment, protons and atomic nuclei are whizzing through our galaxy, sometimes at nearly the speed of light. These charged particles — cosmic rays —span a wide range of energies, with the most energetic packing the same punch as a 90 kilometer-per-hour (56 mph) baseball!
More modest cosmic rays reach “only” peta-electron-volt (PeV) energies — that’s 1015 eV, still more than 100 times more energetic than the particles accelerated by the record-holding Large Hadron Collider. We think that these PeV particles were produced somewhere within our own galaxy.
If we could unravel their secrets, these cosmic rays could provide clues about how stars evolve and ...