Where did the ‘Oh-My-God’ particle come from?

This Scientific American piece by Phil Plait, a professional astronomer and established science communicator, presents well-researched reporting on an actual 1991 cosmic ray detection with strong pedagogical clarity. The article accurately explains the physics (Fermi acceleration, Doppler shift, GZK cutoff limitations) with proper attribution to detector technology and current scientific hypotheses, though it appropriately hedges unknowns—the origin and composition of the OMG particle remain genuinely unresolved. Readers should note this is science journalism covering an enduring mystery rather than a solved question; the article excels at explaining why the particle is puzzling, but the final answer of whether it's a proton or heavier nucleus is appropriately left open, reflecting the state of current knowledge.