A highly energetic atomic nucleus or other particle traveling through space at a speed approaching that of light.
- This radioactive isotope is created when energetic particles in cosmic rays enter the Earth's atmosphere and split atomic nuclei of nitrogen and oxygen.
- Other sources that contribute to the near-Earth space environment include galactic cosmic ray particles, which originate from outside of the solar system.
- The Moon's regolith was created by the ceaseless bombardment of micrometeorites, cosmic rays and particles of solar wind breaking down rocks for billions of years.
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Syllabification: cos·mic ray
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