A substantial directional anisotropy is observed for ultrahigh-energy cosmic rays Cosmic rays are nuclei that have been accelerated to relativistic velocities by astrophysical sources, arriving at Earth after traversing the space between us and the source. As electrically charged particles, they are deflected by magnetic fields, which scramble their directions in space (1). Finding deviations from the highly isotropic angular distribution of high-energy cosmic rays in the sky has long been a prime goal of cosmic-ray researchers. Marginal detections have been reported in the past that failed to hold up. On page 1266 of this issue, The Pierre Auger Collaboration (2) report a strong detection of a pronounced anisotropy in the arrival directions of cosmic rays with energies (E) of ≥8 EeV (8 × 1018 electron volts), indicating that they are of extragalactic origin.

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宇宙射线的新角度

观察到超高能宇宙射线具有显着的方向各向异性 宇宙射线是被天体物理源加速到相对论速度的原子核，穿过我们和源之间的空间后到达地球。作为带电粒子，它们会被磁场偏转，磁场会扰乱它们在空间中的方向 (1)。长期以来，宇宙射线研究人员的主要目标是寻找天空中高能宇宙射线高度各向同性角分布的偏差。过去曾有报道称，边缘检测未能成立。在本期第 1266 页，皮埃尔俄歇合作组织 (2) 报告了在能量 (E) ≥ 8 EeV（8 × 1018 电子伏特）的宇宙射线到达方向上强烈检测到明显的各向异性，