The most powerful cosmic rays raining down on Earth may come not from distant corners of the universe but from heavy dark matter particles that annihilate themselves in our own backyard.
Cosmic rays are high-energy particles that constantly stream through the cosmos. They are largely made of protons, but they can occasionally be made of the nuclei of heavy elements, such as helium and even iron. Despite being microscopic, they pack a punch. Each one travels at nearly the speed of light, and the fastest ones have energies trillions of times stronger than our most powerful particle accelerators.
