The phrase "energy particles" refers to very tiny units of energy. These particles are like tiny bundles of energy that can move and interact with other particles. Full definition
These high energy particles are called cosmic rays and studying them could help physicists understand the universe outside of our solar system. (news.stlpublicradio.org)
Where do cosmic rays come from, and what makes them the highest - energy particles in the universe? (discovermagazine.com)
Although we often think of space as empty, there are loads of high - energy particles shooting through the void. (extremetech.com)