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Why do intergalactic magnetic fields make it hard to trace cosmic rays to their sources?

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Intergalactic magnetic fields make it difficult to trace cosmic rays to their specific sources because these fields are strong enough to deflect the paths of most charged cosmic ray particles during their transit through space.1

Because these particles are electrically charged, they do not travel in straight lines from their points of origin; instead, they follow curved paths influenced by the magnetic fields they encounter. As a result, their arrival directions at Earth do not point back to their precise sources.1

In contrast, gamma rays are not affected by magnetic fields because they are neutral. Consequently, their arrival directions can be used to identify energetic cosmic objects, such as supernova remnants or active galaxies, which may also serve as sources for cosmic ray particles.1