https://www.nature.com/articles/s41586-021-03498-z Skip to main content Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. Advertisement Advertisement Nature * View all journals * Search * My Account Login * Explore content * About the journal * Publish with us Subscribe * Sign up for alerts * RSS feed 1. nature 2. articles 3. article * Article * Published: 17 May 2021 Ultrahigh-energy photons up to 1.4 petaelectronvolts from 12 g-ray Galactic sources * Zhen Cao ORCID: orcid.org/0000-0002-4858-6130^1,2,3, * F. A. Aharonian ORCID: orcid.org/0000-0003-1157-3915^4,5, * Q. An^6,7, * Axikegu^8, * L. X. Bai^9, * Y. X. Bai^1,2, * Y. W. Bao ORCID: orcid.org/0000-0001-8918-5248^10, * D. Bastieri ORCID: orcid.org/0000-0002-6954-8862^11, * X. J. Bi^1,2,3, * Y. J. Bi^1,2, * H. Cai^12, * J. T. Cai^11, * Zhe Cao^6,7, * J. Chang^13, * J. F. Chang^6,1,2, * X. C. Chang^1,2, * B. M. Chen^14, * J. Chen^9, * L. Chen^1,2,3, * Liang Chen^15, * Long Chen^8, * M. J. Chen^1,2, * M. L. Chen^6,1,2, * Q. H. Chen^8, * S. H. Chen^1,2,3, * S. Z. Chen ORCID: orcid.org/0000-0003-0703-1275^1,2, * T. L. Chen^16, * X. L. Chen^1,2,3, * Y. Chen ORCID: orcid.org/0000-0002-4753-2798^10, * N. Cheng^1,2, * Y. D. Cheng ORCID: orcid.org/0000-0003-3891-9461^1,2, * S. W. Cui^14, * X. H. Cui ORCID: orcid.org/0000-0002-6322-7582^17, * Y. D. Cui^18, * B. Z. Dai^19, * H. L. Dai^1,2,13, * Z. G. Dai^10, * Danzengluobu^16, * D. della Volpe^20, * B. D'Ettorre Piazzoli^21, * X. J. Dong^1,2, * J. H. Fan^11, * Y. Z. Fan ORCID: orcid.org/0000-0002-8966-6911^13, * Z. X. Fan^1,2, * J. Fang^19, * K. Fang^1,2, * C. F. Feng^22, * L. Feng^13, * S. H. Feng^1,2, * Y. L. Feng^13, * B. Gao^1,2, * C. D. Gao^22, * Q. Gao^16, * W. Gao ORCID: orcid.org/0000-0003-0656-8572^22, * M. M. Ge ORCID: orcid.org/0000-0002-9680-6804^19, * L. S. Geng^1,2, * G. H. Gong^23, * Q. B. Gou^1,2, * M. H. Gu^6,1,2, * J. G. Guo ORCID: orcid.org/0000-0001-9039-1452^1,2,3, * X. L. Guo^8, * Y. Q. Guo^1,2, * Y. Y. Guo ORCID: orcid.org/0000-0001-9297-2461^1,2,3,13, * Y. A. Han^24, * H. H. He ORCID: orcid.org/0000-0002-5963-4281^1,2,3, * H. N. He^13, * J. C. He^1,2,3, * S. L. He^11, * X. B. He^18, * Y. He^8, * M. Heller^20, * Y. K. Hor^18, * C. Hou^1,2, * X. Hou^25, * H. B. Hu^1,2,3, * S. Hu^9, * S. C. Hu^1,2,3, * X. J. Hu^23, * D. H. Huang^8, * Q. L. Huang^1,2, * W. H. Huang^22, * X. T. Huang^22, * Z. C. Huang^8, * F. Ji^1,2, * X. L. Ji^6,1,2, * H. Y. Jia^8, * K. Jiang^6,7, * Z. J. Jiang^19, * C. Jin^1,2,3, * D. Kuleshov^26, * K. Levochkin^26, * B. B. Li^14, * Cong Li^1,2, * Cheng Li^6,7, * F. Li ORCID: orcid.org/0000-0001-7427-0730^6,1,2, * H. B. Li^1,2, * H. C. Li^1,2, * H. Y. Li^7,13, * J. Li^6,1,2, * K. Li^1,2, * W. L. Li^22, * X. Li^6,7, * Xin Li^8, * X. R. Li^1,2, * Y. Li^9, * Y. Z. Li^1,2,3, * Zhe Li^1,2, * Zhuo Li^27, * E. W. Liang^28, * Y. F. Liang^28, * S. J. Lin^18, * B. Liu ORCID: orcid.org/0000-0002-5965-5576^7, * C. Liu^1,2, * D. Liu^22, * H. Liu^8, * H. D. Liu^24, * J. Liu^1,2, * J. L. Liu^29,30, * J. S. Liu^18, * J. Y. Liu^1,2, * M. Y. Liu^16, * R. Y. Liu ORCID: orcid.org/0000-0003-1576-0961^10, * S. M. Liu ORCID: orcid.org/0000-0003-1039-9521^13, * W. Liu^1,2, * Y. N. Liu^23, * Z. X. Liu^9, * W. J. Long^8, * R. Lu^19, * H. K. Lv^1,2, * B. Q. Ma ORCID: orcid.org/0000-0002-5660-1070^27, * L. L. Ma^1,2, * X. H. Ma^1,2, * J. R. Mao^25, * A. Masood^8, * W. Mitthumsiri^31, * T. Montaruli^20, * Y. C. Nan^22, * B. Y. Pang^8, * P. Pattarakijwanich^31, * Z. Y. Pei^11, * M. Y. Qi^1,2, * D. Ruffolo ORCID: orcid.org/0000-0003-3414-9666^31, * V. Rulev^26, * A. Saiz ORCID: orcid.org/0000-0001-7771-4341^31, * L. Shao ORCID: orcid.org/0000-0001-8876-2357^14, * O. Shchegolev^26,32, * X. D. Sheng^1,2, * J. R. Shi^1,2, * H. C. Song^27, * Yu. V. Stenkin^26,32, * V. Stepanov^26, * Q. N. Sun^8, * X. N. Sun^28, * Z. B. Sun^33, * P. H. T. Tam ORCID: orcid.org/0000-0002-1262-7375^18, * Z. B. Tang ORCID: orcid.org/0000-0002-4247-0081^6,7, * W. W. Tian^3,17, * B. D. Wang^1,2, * C. Wang^33, * H. Wang^8, * H. G. Wang^11, * J. C. Wang^25, * J. S. Wang ORCID: orcid.org/0000-0002-2662-6912^29,30, * L. P. Wang^22, * L. Y. Wang^1,2, * R. N. Wang^8, * W. Wang ORCID: orcid.org/0000-0003-3901-8403^18, * W. Wang^12, * X. G. Wang^28, * X. J. Wang^1,2, * X. Y. Wang^10, * Y. D. Wang^1,2, * Y. J. Wang^1,2, * Y. P. Wang^1,2,3, * Zheng Wang^6,1,2, * Zhen Wang^29,30, * Z. H. Wang^9, * Z. X. Wang^19, * D. M. Wei ORCID: orcid.org/0000-0002-9758-5476^13, * J. J. Wei^13, * Y. J. Wei^1,2,3, * T. Wen^19, * C. Y. Wu^1,2, * H. R. Wu^1,2, * S. Wu^1,2, * W. X. Wu^8, * X. F. Wu^13, * S. Q. Xi^8, * J. Xia^7,13, * J. J. Xia^8, * G. M. Xiang^3,15, * G. Xiao^1,2, * H. B. Xiao ORCID: orcid.org/0000-0001-8244-1229^11, * G. G. Xin^12, * Y. L. Xin^8, * Y. Xing^15, * D. L. Xu^29,30, * R. X. Xu^27, * L. Xue^22, * D. H. Yan^25, * C. W. Yang^9, * F. F. Yang^6,1,2, * J. Y. Yang^18, * L. L. Yang^18, * M. J. Yang^1,2, * R. Z. Yang^7, * S. B. Yang^19, * Y. H. Yao^9, * Z. G. Yao^1,2, * Y. M. Ye^23, * L. Q. Yin^1,2, * N. Yin^22, * X. H. You^1,2, * Z. Y. You^1,2,3, * Y. H. Yu^22, * Q. Yuan^13, * H. D. Zeng^13, * T. X. Zeng^6,1,2, * W. Zeng^19, * Z. K. Zeng^1,2,3, * M. Zha^1,2, * X. X. Zhai^1,2, * B. B. Zhang ORCID: orcid.org/0000-0003-4111-5958^10, * H. M. Zhang ORCID: orcid.org/0000-0001-6863-5369^10, * H. Y. Zhang ORCID: orcid.org/0000-0003-2585-7652^22, * J. L. Zhang^17, * J. W. Zhang^9, * L. Zhang^14, * Li Zhang^19, * L. X. Zhang^11, * P. F. Zhang^19, * P. P. Zhang^14, * R. Zhang^7,13, * S. R. Zhang^14, * S. S. Zhang^1,2, * X. Zhang ORCID: orcid.org/0000-0002-9392-547X^10, * X. P. Zhang^1,2, * Yong Zhang ORCID: orcid.org/0000-0001-6223-4724^1,2, * Yi Zhang^1,13, * Y. F. Zhang^8, * Y. L. Zhang^1,2, * B. Zhao^8, * J. Zhao^1,2, * L. Zhao^6,7, * L. Z. Zhao^14, * S. P. Zhao^13,22, * F. Zheng^33, * Y. Zheng^8, * B. Zhou^1,2, * H. Zhou^29,30, * J. N. Zhou^15, * P. Zhou^10, * R. Zhou^9, * X. X. Zhou^8, * C. G. Zhu^22, * F. R. Zhu^8, * H. Zhu^17, * K. J. Zhu ORCID: orcid.org/0000-0002-5473-235X^6,1,2,3 & * X. Zuo^1,2 Nature volume 594, pages 33-36 (2021)Cite this article * 15k Accesses * 50 Citations * 685 Altmetric * Metrics details Subjects * High-energy astrophysics * Particle astrophysics Abstract The extension of the cosmic-ray spectrum beyond 1 petaelectronvolt (PeV; 10^15 electronvolts) indicates the existence of the so-called PeVatrons--cosmic-ray factories that accelerate particles to PeV energies. We need to locate and identify such objects to find the origin of Galactic cosmic rays^1. The principal signature of both electron and proton PeVatrons is ultrahigh-energy (exceeding 100 TeV) g radiation. Evidence of the presence of a proton PeVatron has been found in the Galactic Centre, according to the detection of a hard-spectrum radiation extending to 0.04 PeV (ref. ^2). Although g-rays with energies slightly higher than 0.1 PeV have been reported from a few objects in the Galactic plane^3,4,5,6, unbiased identification and in-depth exploration of PeVatrons requires detection of g-rays with energies well above 0.1 PeV. Here we report the detection of more than 530 photons at energies above 100 teraelectronvolts and up to 1.4 PeV from 12 ultrahigh-energy g-ray sources with a statistical significance greater than seven standard deviations. Despite having several potential counterparts in their proximity, including pulsar wind nebulae, supernova remnants and star-forming regions, the PeVatrons responsible for the ultrahigh-energy g-rays have not yet been firmly localized and identified (except for the Crab Nebula), leaving open the origin of these extreme accelerators. Access through your institution Buy or subscribe This is a preview of subscription content Access options Access through your institution Access through your institution Change institution Buy or subscribe Subscribe to nature+ Get immediate online access to the entire Nature family of 50+ journals $29.99 monthly Subscribe Subscribe to Journal Get full journal access for 1 year $199.00 only $3.90 per issue Subscribe All prices are NET prices. VAT will be added later in the checkout. Tax calculation will be finalised during checkout. Buy article Get time limited or full article access on ReadCube. $32.00 Buy All prices are NET prices. 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We thank all staff members who work year-round at the LHAASO site at 4,400 m above sea level to maintain the detector and keep the electricity power supply and other components of the experiment operating smoothly. We are grateful to Chengdu Management Committee of Tianfu New Area for constant financial support to research with LHAASO data. Author information Affiliations 1. Key Laboratory of Particle Astrophysics & Experimental Physics Division & Computing Center, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, China Zhen Cao, Y. X. Bai, X. J. Bi, Y. J. Bi, J. F. Chang, X. C. Chang, L. Chen, M. J. Chen, M. L. Chen, S. H. Chen, S. Z. Chen, X. L. Chen, N. Cheng, Y. D. Cheng, H. L. Dai, X. J. Dong, Z. X. Fan, K. Fang, S. H. Feng, B. Gao, L. S. Geng, Q. B. Gou, M. H. Gu, J. G. Guo, Y. Q. Guo, Y. Y. Guo, H. H. He, J. C. He, C. Hou, H. B. Hu, S. C. Hu, Q. L. Huang, F. Ji, X. L. Ji, C. Jin, Cong Li, F. Li, H. B. Li, H. C. Li, J. Li, K. Li, X. R. Li, Y. Z. Li, Zhe Li, C. Liu, J. Liu, J. Y. Liu, W. Liu, H. K. Lv, L. L. Ma, X. H. Ma, M. Y. Qi, X. D. Sheng, J. R. Shi, B. D. Wang, L. Y. Wang, X. J. Wang, Y. D. Wang, Y. J. Wang, Y. P. Wang, Zheng Wang, Y. J. Wei, C. Y. Wu, H. R. Wu, S. Wu, G. Xiao, F. F. Yang, M. J. Yang, Z. G. Yao, L. Q. Yin, X. H. You, Z. Y. You, T. X. Zeng, Z. K. Zeng, M. Zha, X. X. Zhai, S. S. Zhang, X. P. Zhang, Yong Zhang, Yi Zhang, Y. L. Zhang, J. Zhao, B. Zhou, K. J. Zhu & X. Zuo 2. TIANFU Cosmic Ray Research Center, Chengdu, Sichuan, China Zhen Cao, Y. X. Bai, X. J. Bi, Y. J. Bi, J. F. Chang, X. C. Chang, L. Chen, M. J. Chen, M. L. Chen, S. H. Chen, S. Z. Chen, X. L. Chen, N. Cheng, Y. D. Cheng, H. L. Dai, X. J. Dong, Z. X. Fan, K. Fang, S. H. Feng, B. Gao, L. S. Geng, Q. B. Gou, M. H. Gu, J. G. Guo, Y. Q. Guo, Y. Y. Guo, H. H. He, J. C. He, C. Hou, H. B. Hu, S. C. Hu, Q. L. Huang, F. Ji, X. L. Ji, C. Jin, Cong Li, F. Li, H. B. Li, H. C. Li, J. Li, K. Li, X. R. Li, Y. Z. Li, Zhe Li, C. Liu, J. Liu, J. Y. Liu, W. Liu, H. K. Lv, L. L. Ma, X. H. Ma, M. Y. Qi, X. D. Sheng, J. R. Shi, B. D. Wang, L. Y. Wang, X. J. Wang, Y. D. Wang, Y. J. Wang, Y. P. Wang, Zheng Wang, Y. J. Wei, C. Y. Wu, H. R. Wu, S. Wu, G. Xiao, F. F. Yang, M. J. Yang, Z. G. Yao, L. Q. Yin, X. H. You, Z. Y. You, T. X. Zeng, Z. K. Zeng, M. Zha, X. X. Zhai, S. S. Zhang, X. P. Zhang, Yong Zhang, Y. L. Zhang, J. Zhao, B. Zhou, K. J. Zhu & X. Zuo 3. University of Chinese Academy of Sciences, Beijing, China Zhen Cao, X. J. Bi, L. Chen, S. H. Chen, X. L. Chen, J. G. Guo, Y. Y. Guo, H. H. He, J. C. He, H. B. Hu, S. C. Hu, C. Jin, Y. Z. Li, W. W. Tian, Y. P. Wang, Y. J. Wei, G. M. Xiang, Z. Y. You, Z. K. Zeng & K. J. Zhu 4. Dublin Institute for Advanced Studies, Dublin, Ireland F. A. Aharonian 5. Max-Planck-Institut for Nuclear Physics, Heidelberg, Germany F. A. Aharonian 6. State Key Laboratory of Particle Detection and Electronics, Beijing, China Q. An, Zhe Cao, J. F. Chang, M. L. Chen, M. H. Gu, X. L. Ji, K. Jiang, Cheng Li, F. Li, J. Li, X. Li, Z. B. Tang, Zheng Wang, F. F. Yang, T. X. Zeng, L. Zhao & K. J. Zhu 7. University of Science and Technology of China, Hefei, China Q. An, Zhe Cao, K. Jiang, Cheng Li, H. Y. Li, X. Li, B. Liu, Z. B. Tang, J. Xia, R. Z. Yang, R. Zhang & L. Zhao 8. School of Physical Science and Technology & School of Information Science and Technology, Southwest Jiaotong University, Chengdu, China Axikegu, Long Chen, Q. H. Chen, X. L. Guo, Y. He, D. H. Huang, Z. C. Huang, H. Y. Jia, Xin Li, H. Liu, W. J. Long, A. Masood, B. Y. Pang, Q. N. Sun, H. Wang, R. N. Wang, W. X. Wu, S. Q. Xi, J. J. Xia, Y. L. Xin, Y. F. Zhang, B. Zhao, Y. Zheng, X. X. Zhou & F. R. Zhu 9. College of Physics, Sichuan University, Chengdu, China L. X. Bai, J. Chen, S. Hu, Y. Li, Z. X. Liu, Z. H. Wang, C. W. Yang, Y. H. Yao, J. W. Zhang & R. Zhou 10. School of Astronomy and Space Science, Nanjing University, Nanjing, China Y. W. Bao, Y. Chen, Z. G. Dai, R. Y. Liu, X. Y. Wang, B. B. Zhang, H. M. Zhang, X. Zhang & P. Zhou 11. Center for Astrophysics, Guangzhou University, Guangzhou, China D. Bastieri, J. T. Cai, J. H. Fan, S. L. He, Z. Y. Pei, H. G. Wang, H. B. Xiao & L. X. Zhang 12. School of Physics and Technology, Wuhan University, Wuhan, China H. Cai, W. Wang & G. G. Xin 13. Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing, China J. Chang, H. L. Dai, Y. Z. Fan, L. Feng, Y. L. Feng, Y. Y. Guo, H. N. He, H. Y. Li, S. M. Liu, D. M. Wei, J. J. Wei, X. F. Wu, J. Xia, Q. Yuan, H. D. Zeng, R. Zhang, Yi Zhang & S. P. Zhao 14. Hebei Normal University, Shijiazhuang, China B. M. Chen, S. W. Cui, B. B. Li, L. Shao, L. Zhang, P. P. Zhang, S. R. Zhang & L. Z. Zhao 15. Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai, China Liang Chen, G. M. Xiang, Y. Xing & J. N. Zhou 16. Key Laboratory of Cosmic Rays (Tibet University), Ministry of Education, Lhasa, Tibet, China T. L. Chen, Danzengluobu, Q. Gao & M. Y. Liu 17. National Astronomical Observatories, Chinese Academy of Sciences, Beijing, China X. H. Cui, W. W. Tian, J. L. Zhang & H. Zhu 18. School of Physics and Astronomy & School of Physics (Guangzhou), Sun Yat-sen University, Zhuhai, China Y. D. Cui, X. B. He, Y. K. Hor, S. J. Lin, J. S. Liu, P. H. T. Tam, W. Wang, J. Y. Yang & L. L. Yang 19. School of Physics and Astronomy, Yunnan University, Kunming, China B. Z. Dai, J. Fang, M. M. Ge, Z. J. Jiang, R. Lu, Z. X. Wang, T. Wen, S. B. Yang, W. Zeng, Li Zhang & P. F. Zhang 20. Departement de Physique Nucleaire et Corpusculaire, Faculte de Sciences, Universite de Geneve, Geneva, Switzerland D. della Volpe, M. Heller & T. Montaruli 21. Dipartimento di Fisica dell'Universita di Napoli "Federico II", Complesso Universitario di Monte Sant'Angelo, Naples, Italy B. D'Ettorre Piazzoli 22. Institute of Frontier and Interdisciplinary Science, Shandong University, Qingdao, China C. F. Feng, C. D. Gao, W. Gao, W. H. Huang, X. T. Huang, W. L. Li, D. Liu, Y. C. Nan, L. P. Wang, L. Xue, N. Yin, Y. H. Yu, H. Y. Zhang, S. P. Zhao & C. G. Zhu 23. Department of Engineering Physics, Tsinghua University, Beijing, China G. H. Gong, X. J. Hu, Y. N. Liu & Y. M. Ye 24. School of Physics and Microelectronics, Zhengzhou University, Zhengzhou, China Y. A. Han & H. D. Liu 25. Yunnan Observatories, Chinese Academy of Sciences, Kunming, China X. Hou, J. R. Mao, J. C. Wang & D. H. Yan 26. Institute for Nuclear Research of Russian Academy of Sciences, Moscow, Russia D. Kuleshov, K. Levochkin, V. Rulev, O. Shchegolev, Yu. V. Stenkin & V. Stepanov 27. School of Physics, Peking University, Beijing, China Zhuo Li, B. Q. Ma, H. C. Song & R. X. Xu 28. School of Physical Science and Technology, Guangxi University, Nanning, China E. W. Liang, Y. F. Liang, X. N. Sun & X. G. Wang 29. Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai, China J. L. Liu, J. S. Wang, Zhen Wang, D. L. Xu & H. Zhou 30. School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, China J. L. Liu, J. S. Wang, Zhen Wang, D. L. Xu & H. Zhou 31. Department of Physics, Faculty of Science, Mahidol University, Bangkok, Thailand W. Mitthumsiri, P. Pattarakijwanich, D. Ruffolo & A. Saiz 32. Moscow Institute of Physics and Technology, Moscow, Russia O. Shchegolev & Yu. V. Stenkin 33. National Space Science Center, Chinese Academy of Sciences, Beijing, China Z. B. Sun, C. Wang & F. Zheng Authors 1. Zhen Cao View author publications You can also search for this author in PubMed Google Scholar 2. F. A. Aharonian View author publications You can also search for this author in PubMed Google Scholar 3. Q. An View author publications You can also search for this author in PubMed Google Scholar 4. 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Zuo View author publications You can also search for this author in PubMed Google Scholar Contributions This work is the result of the contributions and efforts of all members and institutes of the LHAASO Collaboration under the leadership of Zhen Cao, who is the spokesperson of the LHAASO collaboration. Most of the listed 32 institutes participate in the construction of the LHAASO detectors. In particular, H.H.H. leads the design and construction of KM2A, whose scintillator detector array is constructed by teams led by X.D.S. and muon detector array is constructed by teams led by G.X. KM2A is operated by teams led by J.L. and X. Zuo. The calibration of LHAASO detectors is led by H.H.H. with the participation of groups from IHEP, led by H.K.L. and X. Zuo; from Shandong University, led by C.F.F.; from the University of Science and Technology of China, led by C. Li; and from Southwest Jiaotong University, led by H.Y.J. The CR event reconstruction is led by S.Z.C. with the participation of groups from IHEP, Shandong University and Southwest Jiaotong University. The data analysis by groups from IHEP and Shandong University is led by S.Z.C.; from Sun Yat-sen University by P.H.T.T.; and from the University of Science and Technology of China by R.Z.Y. The team at Purple Mt Observatory, led by Yi Zhang, performs an independent cross-check of the analysis. R.Z.Y. and R.Y.L. lead the interpretation of the results, with participation of the groups from Nanjing University, led by Y.C. and X.Y.W.; from Yunan University, led by L. Zhang; from Purple Mt Observatory, led by Q.Y. Zhen Cao, F.A.A. and B.D.P. supervised the data analysis and interpretation and also lead the paper writing. S.M.L. and D.d.V. contribute as co-chairs of the editorial board of LHAASO. Many groups participated in the analysis procedures, including the groups from Mahidol University, led by D.R.; from Shanghai Jiaotong University, led by H. Zhou; from Shanghai Observatory, led by Z.X.W.; from Peking University, led by Zhuo Li; from Guangxi University, led by E.W.L.; from National Observatory, led by W.W.T.; from Wuhan University, led by P. H. T. Tam; and from Yunnan Observatory, led by J.C.W. All other groups--from the University of Chinese Academy of Science and Tianfu Cosmic ray Research Center, led by Zhen Cao; from State Key Laboratory of Particle Detection and Electronics, led by Q.A.; from Tsinghua University, led by Y.N.L.; from the National Space Science Center, led by Z.B.S.; from Guangzhou University, led by J.H.F.; from Hebei Normal University, led by S.W.C.; from Zhengzhou University, led by H.D.L.; from Sichuan University, led by C.W.Y.; from Tibet University, led by T.L.C.; and from the Institute for Nuclear Research and Moscow Institute of Physics and Technology, led by Yu.V.S.--contributed to detector construction and to reviewing the final version before submission. Corresponding authors Correspondence to Zhen Cao, F. A. Aharonian, S. Z. Chen, R. Y. Liu or R. Z. Yang. Ethics declarations Competing interests The authors declare no competing interests. Additional information Peer review information Nature thanks Razmik Mirzoyan and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Peer reviewer reports are available. Publisher's note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Extended data figures and tables Extended Data Fig. 1 Schematic drawing of the LHAASO layout^7. Small red dots indicate the 5,195 scintillator counters, with a spacing of 15 m in the central area of 1 km^2 and of 30 m in the skirt area of 0.3 km^2 of KM2A. Big blue dots indicate the 1,188 muon detectors distributed in the central area with a spacing of 30 m. The three light-blue rectangles in the centre indicate WCDA, of 78,000 m^ 2 in total. Small black rectangles near WCDA indicate 18 telescopes of WFCTA. Extended Data Fig. 2 g-ray energy distributions in SED bins and corresponding bin purity. a, Distributions of thrown-in energies E[true] in the simulation of events that are in the bins, defined by reconstructed energies E[rec] above 10 TeV. The fraction on the vertical axis is defined as (dN/dE [true])/N[i], where N[i] is the total number of events in the ith bin, defined by the reconstructed energy E[rec]. A bin width of D(log E[rec]) = 0.2 is selected, according to the energy resolution of 14% above 100 TeV (ref. ^8). A power-law spectrum proportional to E^-3.09 is assumed here. b, Bin purity, defined as the fraction of events with E[true] in the bin, as a function of E[rec] in the range from 10 TeV to 2.5 PeV. Extended Data Fig. 3 Distributions (dots) of events in the reconstructed energy bins from 10 TeV to 10 PeV. The input (solid grey line) events are generated using the power-law SED determined from the measured SED of the Crab Nebula^8. For each case, the input SED has an artificial cutoff (dashed lines) at the E [cut] values listed in the key. The distributions demonstrate a clear spillover effect by the events in the bins above E[cut]. The effect becomes weaker at higher energies. There is no indication of pollution of the bins above 1 PeV by events at input energies lower than 0.3 PeV. Extended Data Fig. 4 LHAASO sky map at energies above 100 TeV. The circles indicate the positions of known very-high-energy g-ray sources. Extended Data Fig. 5 Phenomenological fits to the g-ray observations of LHAASO J1908+0621, and previous observations of potential counterparts. The inset shows the KM2A significance map, indicating the potential counterparts of the UHE g-ray source. The colour bar shows the significance (\(\sqrt{{\rm{TS}}}\)). The green circle indicates the PSF of LHAASO. The Fermi LAT points for LHAASO J1908+0621 analysed in this work, as well as ARGO^48, HESS^49 and HAWC^4 data, are shown together with the LHAASO measurements. The dotted curve shows the leptonic model of radiation, assuming an injection of electron/ positron pairs according to the pulsar's spin-down behaviour, with a breaking index of 2 and an initial rotation period of 0.04 s. A fraction of 6% of the current spin-down power of the pulsar PSR J1907+0602 at a distance of 2.4 kpc is assumed to be converted to e^+- pairs to support the g-ray emission. The injection spectrum of electrons is assumed to be \(N(E)\propto {E}_{e}^{-1.75}\exp \{-{[{E} _{e}/(800{\rm{TeV}})]}^{2}\}\). The solid curves correspond to the hadronic model of radiation. Two types of energy distributions are assumed for the parent proton population: (i) a single power-law spectrum of parent protons, N(E) [?] E^-1.85exp[-E/(380 TeV)] (thin solid curve); (ii) a broken power-law spectrum with an exponential cutoff of parent protons, with indices 1.2 and 2.7 below and above 25 TeV, respectively, and a cutoff energy of 1.3 PeV (thick solid curve). In the inset sky map, the black diamond shows the position of PSR J1907+0602, the black contours correspond to the location of supernova remnant SNR G40.5-0.5 and the white circle is the position and size of HESS J1908+063. The cyan regions are the dense clumps described in Methods. The average density in the whole g-ray emission region is estimated to be about 10 cm^-3. g-ray absorption due to photon-photon pair production (see Methods) is taken into account in the theoretical curve. Extended Data Fig. 6 g-ray opacity of LHAASO J2226+6057, J1908+0621, J1825-1326 and Crab Nebula. The absorption due to both ISRFs and CMB is taken into account. Extended Data Table 1 Number of on-source events of energy >100 TeV, residual CR background events and corresponding exposure time for the 12 UHE sources Full size table Extended Data Table 2 List of energetic astrophysical objects possibly associated with each LHAASO source Full size table Supplementary information Peer Review File Rights and permissions Reprints and Permissions About this article Verify currency and authenticity via CrossMark Cite this article Cao, Z., Aharonian, F.A., An, Q. et al. Ultrahigh-energy photons up to 1.4 petaelectronvolts from 12 g-ray Galactic sources. Nature 594, 33-36 (2021). https://doi.org/10.1038/s41586-021-03498-z Download citation * Received: 21 October 2020 * Accepted: 26 March 2021 * Published: 17 May 2021 * Issue Date: 03 June 2021 * DOI: https://doi.org/10.1038/s41586-021-03498-z Share this article Anyone you share the following link with will be able to read this content: Get shareable link Sorry, a shareable link is not currently available for this article. Copy to clipboard Provided by the Springer Nature SharedIt content-sharing initiative Further reading * On the surface brightness radial profile of the extended g-ray sources + Rui-Zhi Yang + Bing Liu Science China Physics, Mechanics & Astronomy (2022) * Regimes of cosmic-ray diffusion in Galactic turbulence + P. Reichherzer + L. Merten + E. G. Zweibel SN Applied Sciences (2022) * An ultra-high-energy g-ray telescope at 4,410 m + Zhen Cao Nature Astronomy (2021) * Hunting the strongest accelerators in our Galaxy + Petra Huentemeyer Nature (2021) * LHAASO: A PeVatrons explorer + Felix A. Aharonian Science China Physics, Mechanics & Astronomy (2021) Comments By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate. 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