The High-Speed Journey of Cosmic Rays



Cosmic rays, primarily composed of hydrogen and helium atomic nuclei, are high-energy particles that traverse space at nearly the speed of light. Originating from beyond our solar system, these particles embark on a high-speed journey through the cosmos.

Cosmic Rays and Their Journey to Earth

Upon reaching Earth, cosmic rays don’t make it to the surface intact. Instead, they collide with gases in the upper atmosphere, disintegrating into showers of lower-energy secondary particles. Despite this disintegration, astronomers can glean valuable information about the properties of primary cosmic rays by tracking the speed and distribution of these secondary particles. This is achieved using satellite and balloon-based detectors.

Categories of Cosmic Rays

Cosmic rays fall into distinct categories based on their speed and energy. The majority, referred to as ‘normal’ cosmic rays, travel at speeds approximately 99% of the speed of light. Trillions of these particles bombard Earth every second. Evidence suggests that a significant proportion of these rays are ejected from distant supernovas.

A much rarer population known as ultra-high energy cosmic rays (UHECRs) carry significantly more energy and travel at speeds just a fraction of a per cent below the speed of light itself. The sources of UHECRs appear to align with distant active galaxies, leading some astronomers to propose that they are created by rapidly spinning supermassive black holes acting as natural particle accelerators.


The study of cosmic rays provides a fascinating insight into the high-energy processes occurring in distant corners of our universe. From their creation in supernovas or around supermassive black holes to their high-speed journey through space and eventual arrival at Earth, cosmic rays continue to be a rich source of scientific discovery.

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