Cosmic rays and astroparticles

Cosmic rays and astroparticles are high-energy particles and related phenomena originating in space. Their study examines their sources, propagation, and interactions with matter.

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Cosmic-ray acceleration: Physical processes that increase charged particles’ energies in astrophysical environments. Explains how candidate sources can produce particles at observed energies.
Supernova remnant: The expanding debris and shocked surroundings left by a supernova explosion. Its shocks are candidate sources of Galactic cosmic rays.
Proton: A positively charged subatomic particle found in atomic nuclei. Protons make up most primary cosmic rays measured near Earth.
Neutrino astronomy: The study of astronomical sources using neutrinos detected on Earth. It can identify cosmic accelerators through particles that travel largely unimpeded from their sources.
Greisen–Zatsepin–Kuzmin limit: The expected energy attenuation of ultra-high-energy cosmic rays interacting with the cosmic microwave background. It constrains how far the most energetic particles can travel from their sources.
Diffusive shock acceleration: A process that energizes charged particles through repeated crossings of a shock front. It is a leading mechanism for accelerating particles at supernova-remnant shocks.
Pulsar wind nebula: A nebula powered by a rapidly rotating neutron star’s magnetized outflow. Its energetic particles provide a nearby-source possibility for cosmic-ray electrons and positrons.
Cosmic-ray electron: A high-energy electron arriving at Earth from space. Its energy spectrum probes nearby accelerators because electrons lose energy rapidly in transit.
Gamma-ray astronomy: The study of celestial objects and processes through gamma-ray observations. It maps high-energy environments and helps identify cosmic-ray interactions.
Cosmic-ray knee: The steepening of the cosmic-ray energy spectrum near a few petaelectronvolts. Its cause may reveal the maximum energies of Galactic accelerators or changes in propagation.