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Cosmic Ray ○꠹｜Definition｜1st｜20251119205401-00-⌔

Cosmic ray - Wikipedia

Cosmic ray

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Cosmic rays or astroparticles are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from outside the Solar System — from the Milky Way,1 from distant galaxies,2 and from the Sun. Upon impact with Earth’s atmosphere, cosmic rays produce showers of secondary particles, some of which reach the surface, although the bulk are deflected into space by Earth’s magnetic field (the magnetosphere) or by the heliosphere.

Cosmic rays were discovered by Victor Hess in 1912 in balloon experiments, for which he was awarded the 1936 Nobel Prize in Physics.3

Direct measurement of cosmic rays, especially at lower energies, has been possible since the first satellites in the late 1950s. Particle detectors similar to those used in nuclear and high-energy physics are used on satellites and space probes for research into cosmic rays.4 Data from the Fermi Space Telescope (2013)5 have been interpreted as evidence that a significant fraction of primary cosmic rays originate from the supernova explosions of stars.6 Based on observations of neutrinos and gamma rays from blazar TXS 0506+056 in 2018, active galactic nuclei also appear to produce cosmic rays.78

Printed 2026-06-28.

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Footnotes

  1. Sharma, Shatendra (2008). Atomic and Nuclear Physics. Pearson Education India. p. 478. ISBN 978-81-317-1924-4. ↩

  2. “Detecting cosmic rays from a galaxy far, far away”. Science Daily. 21 September 2017. Retrieved 26 December 2017. ↩

  3. “Nobel Prize in Physics 1936 – Presentation Speech”. Nobelprize.org. 10 December 1936. Retrieved 27 February 2013. ↩

  4. Cilek, Vaclav, ed. (2009). “Cosmic Influences on the Earth”. Earth System: History and Natural Variability. Vol. I. Eolss Publishers. p. 165. ISBN 978-1-84826-104-4. ↩

  5. Ackermann, M.; Ajello, M.; Allafort, A.; Baldini, L.; Ballet, J.; Barbiellini, G.; et al. (15 February 2013). “Detection of the characteristic pion decay-signature in supernova remnants”. Science. 339 (6424): 807–811. arXiv:1302.3307. Bibcode:2013Sci…339..807A. doi:10.1126/science.1231160. PMID 23413352. S2CID 29815601. ↩

  6. Pinholster, Ginger (13 February 2013). “Evidence shows that cosmic rays come from exploding stars” (Press release). Washington, DC: American Association for the Advancement of Science. ↩

  7. Abramowski, A.; et al. (HESS Collaboration) (2016). “Acceleration of petaelectronvolt protons in the Galactic Centre”. Nature. 531 (7595): 476–479. arXiv:1603.07730. Bibcode:2016Natur.531..476H. doi:10.1038/nature17147. PMID 26982725. S2CID 4461199. ↩

  8. Aartsen, Mark; et al. (IceCube Collaboration) (12 July 2018). “Neutrino emission from the direction of the blazar TXS 0506+056 prior to the IceCube-170922A alert”. Science. 361 (6398): 147–151. arXiv:1807.08794. Bibcode:2018Sci…361..147I. doi:10.1126/science.aat2890. ISSN 0036-8075. PMID 30002248. S2CID 133261745. ↩

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