Loading…
Loading contentLoading…
Loading contentA theoretical ceiling on the energy of cosmic-ray protons that reach us from far away: above roughly 5×10¹⁹ electronvolts they collide with cosmic-microwave-background photons and lose energy, so the highest-energy cosmic rays must originate relatively nearby. Observatories studying the ultra-high-energy sky test this predicted cutoff.
Facts on this topic will be cited from these primary and reference sources.
Mission data, planetary science, space telescopes, and public-domain imagery.
Most NASA-produced imagery is in the public domain; individual items are checked for usage terms before publication.