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Cosmic Rays 

As you are reading this sentence, thousands of cosmic rays are passing through your body. They have been your whole life… But what are they exactly?

The composition of cosmic rays is estimated as follows:

• 89% Simple protons
• 10%Alpha particles
• Most of the remaining 1% are electrons, positrons andantiprotons and other heavier nuclei (which are abundant end products of stars’ nuclear synthesis)

(However, the precise composition of cosmic rays outside the Earth’s atmosphere can vary depending on which part of the energy spectrum is observed.) 

There are two types of cosmic rays:

Primary cosmic rays

It is speculated that cosmic rays are formed when particles are accelerated by a blast waves of supernova remnants. They eventually gain so much energy from expanding clouds of gas and bouncing back and forth in magnetic fields that they continue to move through space at speeds very close to that of light. The supernova remnants are not able to contain them when they reach these speeds (and also have energies of over 10¹⁸ eV), so the cosmic rays escape into the galaxy. The maximum amounts of energy cosmic rays can gain depend on the size of the acceleration region and the strength of its magnetic field. 

Secondary cosmic rays

Primary cosmic rays interact with interstellar matter to produce a second type of cosmic ray. Heavy nuclei (mainly carbon and oxygen) that make up less than 1% of cosmic rays break up into lighter nuclei (of mainly lithium, beryllium and boron) upon penetration of the Earth’s atmosphere and surface by a process of cosmic ray spallation.