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A very rapidly moving particle of extraterrestrial origin, especially one that collides with the earth's atmosphere. Cosmic rays are mainly protons and alpha particles but sometimes are other light atomic nuclei and high-energy electrons.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
a radiation of high penetrating power originating in outer space and consisting partly of high-energy atomic nuclei.
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.
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|Noun||1.||cosmic ray - highly penetrating ionizing radiation of extraterrestrial origin; consisting chiefly of protons and alpha particles; collision with atmospheric particles results in rays and particles of many kinds|
ionizing radiation - high-energy radiation capable of producing ionization in substances through which it passes
cosmic radiation - radiation coming from outside the solar system
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