High-energy cosmic rays , which scientists have known about for over 50 years, are like tiny space bullets made of charged particles, ranging from single protons to heavy atomic nuclei like iron. They are extremely energetic and can travel vast distances through the cosmos at nearly the speed of light before reaching Earth.Identifying cosmic ray properties can help astronomers infer important information about the processes that occur within our galaxy and the universe as a whole, including the events that generate them and the structures they travel through to reach us. While lower-energy cosmic rays come from inside the Milky Way — including from our Sun, clusters of stars, and supernova events — the highest-energy cosmic rays have long been believed to originate outside our galaxy.For the study, researchers concentrated their efforts on cosmic rays with energies over 8 x 10electron volts — which is a million times more energy than the Large Hadron Collider (LHC) pumps into a proton, or about as much energy as it takes to lift a laptop one foot above a table.When a high-energy cosmic ray reaches Earth, it can strike and obliterate any unlucky molecule hanging out in our upper atmosphere. This initial collision starts a devastating chain reaction that cascades down through the atmosphere, ripping apart other molecules, producing what is known as an air shower . These air showers balloon out as they descend downward, and by the time they reach the ground, they can cover an area up to 10,000 acres (40 square kilometers) and contain over 10 billion secondary particles — such as electrons, photons, and muons.The Pierre Auger Observatory, located in the Argentinian Pampas, does not detect cosmic rays directly. Instead, it observes the secondary particles from air showers using a massive array of over 1,600 individual detectors spanning nearly 1,200 square miles (3,000 square km).