TY - JOUR IS - 7937 PB - Springer Science and Business Media LLC Y1 - 2022/11/24/ A1 - Liodakis, Ioannis A1 - Marscher, Alan P A1 - Agudo, Iván A1 - Berdyugin, Andrei V A1 - Bernardos, Maria I A1 - Bonnoli, Giacomo A1 - Borman, George A A1 - Casadio, Carolina A1 - Casanova, V? Ctor A1 - Cavazzuti, Elisabetta A1 - Rodriguez Cavero, Nicole A1 - Di Gesu, Laura A1 - Di Lalla, Niccoló A1 - Donnarumma, Immacolata A1 - Ehlert, Steven R A1 - Errando, Manel A1 - Escudero, Juan A1 - Garc? A-Comas, Maya A1 - Ag? S-González, Beatriz A1 - Husillos, César A1 - Jormanainen, Jenni A1 - Jorstad, Svetlana G A1 - Kagitani, Masato A1 - Kopatskaya, Evgenia N A1 - Kravtsov, Vadim A1 - Krawczynski, Henric A1 - Lindfors, Elina A1 - Larionova, Elena G A1 - Madejski, Grzegorz M A1 - Marin, Frédéric A1 - Marchini, Alessandro A1 - Marshall, Herman L A1 - Morozova, Daria A A1 - Massaro, Francesco A1 - Masiero, Joseph R A1 - Mawet, Dimitri A1 - Middei, Riccardo A1 - Millar-Blanchaer, Maxwell A A1 - Myserlis, Ioannis A1 - Negro, Michela A1 - Nilsson, Kari A1 - O'Dell, Stephen L A1 - Omodei, Nicola A1 - Pacciani, Luigi A1 - Paggi, Alessandro A1 - Panopoulou, Georgia V A1 - Peirson, Abel L A1 - Perri, Matteo A1 - Petrucci, Pierre-Olivier A1 - Poutanen, Juri A1 - Puccetti, Simonetta A1 - Romani, Roger W A1 - Sakanoi, Takeshi A1 - Savchenko, Sergey S A1 - Sota, Alfredo A1 - Tavecchio, Fabrizio A1 - Tinyanont, Samaporn A1 - Vasilyev, Andrey A A1 - Weaver, Zachary R A1 - Zhovtan, Alexey V A1 - Antonelli, Lucio A A1 - Bachetti, Matteo A1 - Baldini, Luca A1 - Baumgartner, Wayne H A1 - Bellazzini, Ronaldo A1 - Bianchi, Stefano A1 - Bongiorno, Stephen D A1 - Bonino, Raffaella A1 - Brez, Alessandro A1 - Bucciantini, Niccoló A1 - Capitanio, Fiamma A1 - Castellano, Simone A1 - Ciprini, Stefano A1 - Costa, Enrico A1 - De Rosa, Alessandra A1 - Del Monte, Ettore A1 - Di Marco, Alessandro A1 - Doroshenko, Victor A1 - Dov?iak, Michal A1 - Enoto, Teruaki A1 - Evangelista, Yuri A1 - Fabiani, Sergio A1 - Ferrazzoli, Riccardo A1 - Garcia, Javier A A1 - Gunji, Shuichi A1 - Hayashida, Kiyoshi A1 - Heyl, Jeremy A1 - Iwakiri, Wataru A1 - Karas, Vladimir A1 - Kitaguchi, Takao A1 - Kolodziejczak, Jeffery J A1 - La Monaca, Fabio A1 - Latronico, Luca A1 - Maldera, Simone A1 - Manfreda, Alberto A1 - Marinucci, Andrea A1 - Matt, Giorgio A1 - Mitsuishi, Ikuyuki A1 - Mizuno, Tsunefumi A1 - Muleri, Fabio A1 - Ng, Stephen C-Y A1 - Oppedisano, Chiara A1 - Papitto, Alessandro A1 - Pavlov, George G A1 - Pesce-Rollins, Melissa A1 - Pilia, Maura A1 - Possenti, Andrea A1 - Ramsey, Brian D A1 - Rankin, John A1 - Ratheesh, Ajay A1 - Sgró, Carmelo A1 - Slane, Patrick A1 - Soffitta, Paolo A1 - Spandre, Gloria A1 - Tamagawa, Toru A1 - Taverna, Roberto A1 - Tawara, Yuzuru A1 - Tennant, Allyn F A1 - Thomas, Nicolas E A1 - Tombesi, Francesco A1 - Trois, Alessio A1 - Tsygankov, Sergey A1 - Turolla, Roberto A1 - Vink, Jacco A1 - Weisskopf, Martin C A1 - Wu, Kinwah A1 - Xie, Fei A1 - Zane, Silvia SN - 0028-0836 N1 - Open Access: This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article?s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article?s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. ID - discovery10160826 AV - public EP - 681 JF - Nature N2 - Most of the light from blazars, active galactic nuclei with jets of magnetized plasma that point nearly along the line of sight, is produced by high-energy particles, up to around 1?TeV. Although the jets are known to be ultimately powered by a supermassive black hole, how the particles are accelerated to such high energies has been an unanswered question. The process must be related to the magnetic field, which can be probed by observations of the polarization of light from the jets. Measurements of the radio to optical polarization-the only range available until now-probe extended regions of the jet containing particles that left the acceleration site days to years earlier1-3, and hence do not directly explore the acceleration mechanism, as could X-ray measurements. Here we report the detection of X-ray polarization from the blazar Markarian 501 (Mrk 501). We measure an X-ray linear polarization degree ?X of around 10%, which is a factor of around 2 higher than the value at optical wavelengths, with a polarization angle parallel to the radio jet. This points to a shock front as the source of particle acceleration and also implies that the plasma becomes increasingly turbulent with distance from the shock. VL - 611 SP - 677 UR - https://doi.org/10.1038/s41586-022-05338-0 TI - Polarized blazar X-rays imply particle acceleration in shocks KW - X-Rays KW - Radiography KW - Acceleration KW - Aircraft KW - Cell Nucleus ER -