ultra-high-energy cosmic rays

Ultra-high-energy cosmic rays are extremely energetic particles from space—mainly protons or atomic nuclei—that travel near the speed of light. They originate from some of the universe’s most powerful phenomena, like supermassive black holes or exploding stars. When these particles reach Earth, they create showers of secondary particles in the atmosphere, which scientists detect with special instruments. Studying them helps scientists understand extreme cosmic environments and fundamental physics, as their incredible energies surpass those achievable by human-made accelerators, making them some of the universe's most energetic and mysterious travelers.