Observation of the Shadows of the Moon and Sun Using the Pierre Auger Observatory at an Average Energy of $7\times10^{17}\,$eV
The Pierre Auger Collaboration,
A. Abdul Halim,
P. Abreu,
M. Aglietta,
I. Allekotte,
K. Almeida Cheminant,
A. Almela, R. Aloisio, J. Alvarez-Muñiz, A. Ambrosone, J. Ammerman Yebra, G.A. Anastasi, L.A. Anchordoqui, B. Andrada, L. Andrade Dourado, S. Andringa, L. Apollonio, C. Aramo, E. Arnone, J.C. Arteaga Velazquez, P. Assis, G. Avila, E. Avocone, A. Bakalova, F. Barbato, A. Bartz Mocellin, J.A. Bellido, C. Berat, M.E. Bertaina, M. Bianciotto, P.L. Biermann, V. Binet, K. Bismark, T. Bister, J. Biteau, J. Blazek, J. Blümer, M. Bohacova, D. Boncioli, C. Bonifazi, L. Bonneau Arbeletche, N. Borodai, J. Brack, P.G. Brichetto Orchera, F.L. Briechle, A. Bueno, S. Buitink, M. Buscemi, M. Büsken, A. Bwembya, K.S. Caballero-Mora, S. Cabana-Freire, L. Caccianiga, F. Campuzano, J. Caraça-Valente, R. Caruso, A. Castellina, F. Catalani, G. Cataldi, L. Cazon, M. Cerda, B. Čermáková, A. Cermenati, J.A. Chinellato, J. Chudoba, L. Chytka, R.W. Clay, A. Cobos Cerutti, R. Colalillo, R. Conceição, G. Consolati, M. Conte, F. Convenga, D. Correia dos Santos, P.J. Costa, C. Covault, M. Cristinziani, C.S. Cruz Sanchez, S. Dasso, K. Daumiller, B.R. Dawson, R.M. de Almeida, E.T. de Boone, B. de Errico, J. de Jesús, S.J. de Jong, J. de Mello Neto, I. De Mitri, J. de Oliveira, D. de Oliveira Franco, F. de Palma, V. de Souza, E. De Vito, A. Del Popolo, O. Deligny, N. Denner, L. Deval, A. di Matteo, C. Dobrigkeit, J.C. D'Olivo, L.M. Domingues Mendes, Q. Dorosti, J. dos Anjos, R.C. dos Anjos, J. Ebr, F.H. Ellwanger, R. Engel, I. Epicoco, M. Erdmann, A. Etchegoyen, C. Evoli, H. Falcke, G.R. Farrar, A. Fauth, T. Fehler, F. Feldbusch, A. Fernandes, M. Fernandez, B. Fick, J.M. Figueira, P. Filip, A. Filipcic, T. Fitoussi, B. Flaggs, T. Fodran, A. Franco, M. Freitas, T. Fujii, A. Fuster, C. Galea, B. Garcia, C. Gaudu, P.L. Ghia, U. Giaccari, F. Gobbi, F. Gollan, G. Golup, M. Gómez Berisso, P.F. Gómez Vitale, J.P. Gongora, J.M. Gonzalez, N.M. Gonzalez, D. Gora, A. Gorgi, M. Gottowik, F. Guarino, G. Guedes, L. Gülzow, S. Hahn, P. Hamal, M.R. Hampel, P.M. Hansen, V.M. Harvey, A. Haungs, T. Hebbeker, C. Hojvat, J. Hörandel, P. Horvath, M. Hrabovsky, T. Huege, A. Insolia, P.G. Isar, M. Ismaiel, P. Janecek, V. Jilek, K.H. Kampert, B. Keilhauer, A. Khakurdikar, V.V. Kizakke Covilakam, H. Klages, M. Kleifges, J. Köhler, F. Krieger, M. Kubatova, N. Kunka, B.L. Lago, N. Langner, N. Leal, M.A. Leigui de Oliveira, Y. Lema-Capeans, A. Letessier-Selvon, I. Lhenry-Yvon, L. Lopes, J.P. Lundquist, M. Mallamaci, D. Mandat, P. Mantsch, F.M. Mariani, A. Mariazzi, I.C. Maris, G. Marsella, D. Martello, S. Martinelli, M.A. Martins, H.J. Mathes, J. Matthews, G. Matthiae, E.W. Mayotte, S. Mayotte, P. Mazur, G. Medina-Tanco, J. Meinert, D. Melo, A. Menshikov, C. Merx, S. Michal, M.I. Micheletti, L. Miramonti, M. Mogarkar, S. Mollerach, F. Montanet, L. Morejon, K. Mulrey, R. Mussa, W.M. Namasaka, S. Negi, L. Nellen, K. Nguyen, G. Nicora, M. Niechciol, D. Nitz, D. Nosek, A. Novikov, V. Novotný, L. Nozka, A. Nucita, L.A. Nunez, J. Ochoa, C. Oliveira, L. Östman, M. Palatka, J. Pallotta, S. Panja, G. Parente, T. Paulsen, J. Pawlowsky, M. Pech, J. Pękala, R. Pelayo, V. Pelgrims, L.A. Pereira, E.E. Pereira Martins, C. Pérez Bertolli, L. Perrone, S. Petrera, C. Petrucci, T. Pierog, M. Pimenta, M. Platino, B. Pont, M. Pourmohammad Shahvar, P. Privitera, C. Priyadarshi, M. Prouza, K. Pytel, S. Querchfeld, J. Rautenberg, D. Ravignani, J.V. Reginatto Akim, A. Reuzki, J. Ridky, F. Riehn, M. Risse, V. Rizi, E. Rodriguez, G. Rodriguez Fernandez, J.R. Rodriguez Rojo, S. Rossoni, M. Roth, E. Roulet, A. Rovero, A. Saftoiu, M. Saharan, F. Salamida, H.I. Salazar, G. Salina, P. Sampathkumar, N. San Martin, J. Sanabria Gomez, F.A. Sánchez, E.M. Santos, E. Santos, F. Sarazin, R. Sarmento, R. Sato, P. Savina, V. Scherini, H. Schieler, M. Schimassek, M. Schimp, D. Schmidt, O. Scholten, H. Schoorlemmer, P. Schovanek, F.G. Schröder, J. Schulte, T. Schulz, S.J. Sciutto, M. Scornavacche, A. Sedoski, A. Segreto, S. Sehgal, S.U. Shivashankara, G. Sigl, K. Simkova*, F. Simon, R. Smida, P. Sommers, R. Squartini, M. Stadelmaier, S. Stanič, J. Stasielak, P. Stassi, S. Strähnz, M. Straub, T. Suomijarvi, A.D. Supanitsky, Z. Svozilikova, K. Syrokvas, Z. Szadkowski, F. Tairli, M. Tambone, A. Tapia, C. Taricco, C. Timmermans, O. Tkachenko, P. Tobiska, C.J. Todero Peixoto, B. Tomé, A. Travaini, P. Travnicek, M.J. Tueros, M. Unger, R. Uzeiroska, L. Vaclavek, M. Vacula, I. Vaiman, J.F. Valdés Galicia, L. Valore, P. van Dillen, E. Varela, V. Vašíčková, A. Vásquez-Ramírez, D. Veberic, I.D. Vergara Quispe, S. Verpoest, V. Verzi, J. Vicha, J. Vink, S. Vorobiov, J.B. Vuta, C.K.O. Watanabe, A. Watson, A. Weindl, M. Weitz, L. Wiencke, H. Wilczyński, B. Wundheiler, B. Yue, A. Yushkov, E. Zas, D. Zavrtanik and M. Zavrtaniket al. (click to show)*: corresponding author
Pre-published on:
September 24, 2025
Published on:
December 30, 2025
Abstract
The interaction of cosmic rays with celestial bodies such as the Moon or
the Sun produces a shadow in the arrival direction distribution of the
cosmic rays reaching the Earth. Such deficits from an isotropic flux
have been observed by astroparticle observatories below energies of
$10^{15}\,$eV. Above this energy, measurements were limited due to the
low number of events as a result of the steeply falling cosmic-ray flux
with energy. With more than 10.6 million events recorded during 20 years
of operation of the Pierre Auger Observatory, we report the first
observation of the shadow of the Moon at an average energy of
$7\times10^{17}\,$eV with a maximum significance above 3$\sigma$.
The shadow is an end-to-end check that the celestial directions are correctly reconstructed from the air shower data, and it is used here to derive the effective angular resolution for this dataset. Additionally, we present the results of a similar study on the
shadow of the Sun.
DOI: https://doi.org/10.22323/1.501.0398
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