Final answer:
Primary cosmic rays are high-energy particles predominantly from outside the solar system. They consist of fast-moving atomic nuclei and electrons, and their paths are shaped by magnetic fields which makes their precise origins hard to determine.
Step-by-step explanation:
Primary cosmic rays are high-energy particles from outer space that reach Earth, coming mainly from outside our solar system. These particles are composed mostly of high-speed atomic nuclei and electrons, with about 90% being hydrogen nuclei (protons) and roughly 9% being helium and heavier nuclei. The remaining 1% includes electrons and positrons, with positrons being a form of antimatter. Because cosmic rays are charged particles, their paths can be bent by magnetic fields, making it difficult to trace their exact origins. However, many cosmic rays are believed to be produced in the aftermath of supernova shocks, where the explosive demise of a star accelerates particles to incredibly high speeds.