AWhat changed
On 27 May 2021 Telescope Array recorded an extensive air shower across 23 surface detectors. Its reconstructed primary energy was 244 ± 29 statistical and +51/−76 systematic exaelectronvolts on the fluorescence-calibrated energy scale. The arrival direction and backtracking under selected Galactic magnetic-field models were compared with nearby source distributions.
Scientific scope
On 27 May 2021 Telescope Array recorded an extensive air shower across 23 surface detectors. Its reconstructed primary energy was 244 ± 29 statistical and +51/−76 systematic exaelectronvolts on the fluorescence-calibrated energy scale. The arrival direction and backtracking under selected Galactic magnetic-field models were compared with nearby source distributions. This is one reconstructed air-shower event, not a direct detection of the primary particle in the detector. The fluorescence detectors were inactive because of moonlight; the classifier disfavored a photon under its model but could not distinguish a proton from heavy nuclei. The 244 EeV scale is calibrated from other fluorescence observations; the original surface-detector estimate was 309 ± 37 EeV before normalization. Large energy and composition uncertainties and Galactic/extragalactic magnetic deflections affect source inference. The authors identified no convincing source under their selected models; a Local Void line of sight is not proof of a source in the void or of new physics. Earlier 1991, 1993 and 2001 ultra-high-energy events retain credit. The paper includes supplementary material; the raw event data have not been independently reanalyzed.
Evidence
The linked original works support the scoped statement and contribution attribution. WRS has not independently replayed experiments or reconstructed a full mathematical proof. This is one reconstructed air-shower event, not a direct detection of the primary particle in the detector. The fluorescence detectors were inactive because of moonlight; the classifier disfavored a photon under its model but could not distinguish a proton from heavy nuclei. The 244 EeV scale is calibrated from other fluorescence observations; the original surface-detector estimate was 309 ± 37 EeV before normalization. Large energy and composition uncertainties and Galactic/extragalactic magnetic deflections affect source inference. The authors identified no convincing source under their selected models; a Local Void line of sight is not proof of a source in the void or of new physics. Earlier 1991, 1993 and 2001 ultra-high-energy events retain credit. The paper includes supplementary material; the raw event data have not been independently reanalyzed.
Contributors
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Provisional WRS assessment, edition 2026-10-28.1. Independent expert calibration is pending. This grade does not certify correctness or assign ownership.
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