The Earth is bombarded by ultrarelativistic particles, known as cosmic rays (CRs). CRs with energies up to a few PeV (=10¹⁵ eV), the knee in the particle spectrum, are believed to have a Galactic origin. One or more factories of PeV CRs, or PeVatrons, must thus be active within our Galaxy. The direct detection of PeV protons from their sources is not possible since they are deflected in the Galactic magnetic fields. Hundred TeV γ-rays from decaying π ⁰, produced when PeV CRs collide with the ambient gas, can provide the decisive evidence of proton acceleration up to the knee. Here we report the discovery by the High Altitude Water Cerenkov (HAWC) observatory of the γ-ray source, HAWC J1825-134, whose energy spectrum extends well beyond 200 TeV without a break or cutoff. The source is found to be coincident with a giant molecular cloud. The ambient gas density is as high as 700 protons cm⁻³. While the nature of this extreme accelerator remains unclear, CRs accelerated to energies of several PeV colliding with the ambient gas likely produce the observed radiation.

地球被超相对论粒子轰炸，这就是宇宙射线（CR）。能量高达几个PeV（= 10 ¹⁵ eV）（在粒子光谱中为膝盖）的CR被认为是银河系起源的。因此，一个或多个PeV CR或PeVatrons工厂必须在我们的银河系中活跃起来。由于PeV质子在银河磁场中发生偏转，因此无法直接从其来源检测PeV质子。百TeV的γ射线从腐烂的π ⁰，时产生PEV的CR碰撞环境气体，可提供质子加速至膝盖的决定性的证据。在这里，我们报道了γ的高海拔水切伦科夫（HAWC）天文台的发现射线源HAWC J1825-134，其能谱扩展到200 TeV以上，没有断裂或截止。发现该源与巨大的分子云一致。环境气体密度高达700质子cm ^-3。尽管这种极端加速器的性质尚不清楚，但CR加速到几PeV的能量与周围气体碰撞时，很可能产生观察到的辐射。