First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole
Authors:   The Event Horizon Telescope Collaboration, Akiyama Kazunori , Alberdi Antxon , Alef Walter , Asada Keiichi , Azulay Rebecca , Baczko Anne-Kathrin , Ball David , Baloković Mislav , Barrett John , Bintley Dan , Blackburn Lindy , Boland Wilfred , Bouman Katherine L. , Bower Geoffrey C. , Bremer Michael , Brinkerink Christiaan D. , Brissenden Roger , Britzen Silke , Broderick Avery E. , Broguiere Dominique , Bronzwaer Thomas , Byun Do-Young , Carlstrom John E. , Chael Andrew , Chan Chi-kwan , Chatterjee Shami , Chatterjee Koushik , Chen Ming-Tang , Chen 陈 Yongjun 永军 , Cho Ilje , Christian Pierre , Conway John E. , Cordes James M. , Crew Geoffrey B. , Cui Yuzhu , Davelaar Jordy , Laurentis Mariafelicia De , Deane Roger , Dempsey Jessica , Desvignes Gregory , Dexter Jason , Doeleman Sheperd S. , Eatough Ralph P. , Falcke Heino , Fish Vincent L. , Fomalont Ed , Fraga-Encinas Raquel , Freeman William T. , Friberg Per , Fromm Christian M. , Gómez José L. , Galison Peter , Gammie Charles F. , García Roberto , Gentaz Olivier , Georgiev Boris , Goddi Ciriaco , Gold Roman , Gu 顾 Minfeng 敏峰 , Gurwell Mark , Hada Kazuhiro , Hecht Michael H. , Hesper Ronald , Ho 何 Luis C. 子山 , Ho Paul , Honma Mareki , Huang Chih-Wei L. , Huang 黄 Lei 磊 , Hughes David H. , Ikeda Shiro , Inoue Makoto , Issaoun Sara , James David J. , Jannuzi Buell T. , Janssen Michael , Jeter Britton , Jiang 江 Wu 悟 , Johnson Michael D. , Jorstad Svetlana , Jung Taehyun , Karami Mansour , Karuppusamy Ramesh , Kawashima Tomohisa , Keating Garrett K. , Kettenis Mark , Kim Jae-Young , Kim Junhan , Kim Jongsoo , Kino Motoki , Koay Jun Yi , Koch Patrick M. , Koyama Shoko , Kramer Michael , Kramer Carsten , Krichbaum Thomas P. , Kuo Cheng-Yu , Lauer Tod R. , Lee Sang-Sung , Li 李 Yan-Rong 彦荣 , Li 李 Zhiyuan 志远 , Lindqvist Michael , Liu Kuo , Liuzzo Elisabetta , Lo Wen-Ping , Lobanov Andrei P. , Loinard Laurent , Lonsdale Colin , Lu 路 Ru-Sen 如森 , MacDonald Nicholas R. , Mao 毛 Jirong 基荣 , Markoff Sera , Marrone Daniel P. , Marscher Alan P. , Martí-Vidal Iván , Matsushita Satoki , Matthews Lynn D. , Medeiros Lia , Menten Karl M. , Mizuno Yosuke , Mizuno Izumi , Moran James M. , Moriyama Kotaro , Moscibrodzka Monika , Müller Cornelia , Nagai Hiroshi , Nagar Neil M. , Nakamura Masanori , Narayan Ramesh , Narayanan Gopal , Natarajan Iniyan , Neri Roberto , Ni Chunchong , Noutsos Aristeidis , Okino Hiroki , Olivares Héctor , Ortiz-León Gisela N. , Oyama Tomoaki , Özel Feryal , Palumbo Daniel C. M. , Patel Nimesh , Pen Ue-Li , Pesce Dominic W. , Piétu Vincent , Plambeck Richard , PopStefanija Aleksandar , Porth Oliver , Prather Ben , Preciado-López Jorge A. , Psaltis Dimitrios , Pu Hung-Yi , Ramakrishnan Venkatessh , Rao Ramprasad , Rawlings Mark G. , Raymond Alexander W. , Rezzolla Luciano , Ripperda Bart , Roelofs Freek , Rogers Alan , Ros Eduardo , Rose Mel , Roshanineshat Arash , Rottmann Helge , Roy Alan L. , Ruszczyk Chet , Ryan Benjamin R. , Rygl Kazi L. J. , Sánchez Salvador , Sánchez-Arguelles David , Sasada Mahito , Savolainen Tuomas , Schloerb F. Peter , Schuster Karl-Friedrich , Shao Lijing , Shen 沈 Zhiqiang 志强 , Small Des , Sohn Bong Won , SooHoo Jason , Tazaki Fumie , Tiede Paul , Tilanus Remo P. J. , Titus Michael , Toma Kenji , Torne Pablo , Trent Tyler , Trippe Sascha , Tsuda Shuichiro , Bemmel Ilse van , van Langevelde Huib Jan , van Rossum Daniel R. , Wagner Jan , Wardle John , Weintroub Jonathan , Wex Norbert , Wharton Robert , Wielgus Maciek , Wong George N. , Wu 吴 Qingwen 庆文 , Young Ken , Young André , Younsi Ziri , Yuan 袁 Feng 峰 , Yuan 袁 Ye-Fei 业飞 , Zensus J. Anton , Zhao Guangyao , Zhao Shan-Shan , Zhu Ziyan , Algaba Juan-Carlos , Allardi Alexander , Amestica Rodrigo , Anczarski Jadyn , Bach Uwe , Baganoff Frederick K. , Beaudoin Christopher , Benson Bradford A. , Berthold Ryan , Blanchard Jay M. , Blundell Ray , Bustamente Sandra , Cappallo Roger , Castillo-Domínguez Edgar , Chang Chih-Cheng , Chang Shu-Hao , Chang Song-Chu , Chen Chung-Chen , Chilson Ryan , Chuter Tim C. , Rosado Rodrigo Córdova , Coulson Iain M. , Crawford Thomas M. , Crowley Joseph , David John , Derome Mark , Dexter Matthew , Dornbusch Sven , Dudevoir Kevin A. , Dzib Sergio A. , Eckart Andreas , Eckert Chris , Erickson Neal R. , Everett Wendeline B. , Faber Aaron , Farah Joseph R. , Fath Vernon , Folkers Thomas W. , Forbes David C. , Freund Robert , Gómez-Ruiz Arturo I. , Gale David M. , Gao Feng , Geertsema Gertie , Graham David A. , Greer Christopher H. , Grosslein Ronald , Gueth Frédéric , Haggard Daryl , Halverson Nils W. , Han Chih-Chiang , Han Kuo-Chang , Hao Jinchi , Hasegawa Yutaka , Henning Jason W. , Hernández-Gómez Antonio , Herrero-Illana Rubén , Heyminck Stefan , Hirota Akihiko , Hoge James , Huang Yau-De , Impellizzeri C. M. Violette , Jiang Homin , Kamble Atish , Keisler Ryan , Kimura Kimihiro , Kono Yusuke , Kubo Derek , Kuroda John , Lacasse Richard , Laing Robert A. , Leitch Erik M. , Li Chao-Te , Lin Lupin C.-C. , Liu Ching-Tang , Liu Kuan-Yu , Lu Li-Ming , Marson Ralph G. , Martin-Cocher Pierre L. , Massingill Kyle D. , Matulonis Callie , McColl Martin P. , McWhirter Stephen R. , Messias Hugo , Meyer-Zhao Zheng , Michalik Daniel , Montaña Alfredo , Montgomerie William , Mora-Klein Matias , Muders Dirk , Nadolski Andrew , Navarro Santiago , Neilsen Joseph , Nguyen Chi H. , Nishioka Hiroaki , Norton Timothy , Nowak Michael A. , Nystrom George , Ogawa Hideo , Oshiro Peter , Oyama Tomoaki , Parsons Harriet , Paine Scott N. , Peñalver Juan , Phillips Neil M. , Poirier Michael , Pradel Nicolas , Primiani Rurik A. , Raffin Philippe A. , Rahlin Alexandra S. , Reiland George , Risacher Christopher , Ruiz Ignacio , Sáez-Madaín Alejandro F. , Sassella Remi , Schellart Pim , Shaw Paul , Silva Kevin M. , Shiokawa Hotaka , Smith David R. , Snow William , Souccar Kamal , Sousa Don , Sridharan T. K. , Srinivasan Ranjani , Stahm William , Stark Anthony A. , Story Kyle , Timmer Sjoerd T. , Vertatschitsch Laura , Walther Craig , Wei Ta-Shun , Whitehorn Nathan , Whitney Alan R. , Woody David P. , Wouterloot Jan G. A. , Wright Melvin , Yamaguchi Paul , Yu Chen-Yu , Zeballos Milagros , Zhang Shuo , Ziurys Lucy 
Published: April 2019

Abstract
When surrounded by a transparent emission region, black holes are expected to reveal a dark shadow caused by gravitational light bending and photon capture at the event horizon. To image and study this phenomenon, we have assembled the Event Horizon Telescope, a global very long baseline interferometry array observing at a wavelength of 1.3 mm. This allows us to reconstruct event-horizon-scale images of the supermassive black hole candidate in the center of the giant elliptical galaxy M87. We have resolved the central compact radio source as an asymmetric bright emission ring with a diameter of 42 ± 3 μas, which is circular and encompasses a central depression in brightness with a flux ratio ≳10:1. The emission ring is recovered using different calibration and imaging schemes, with its diameter and width remaining stable over four different observations carried out in different days. Overall, the observed image is consistent with expectations for the shadow of a Kerr black hole as predicted by general relativity. The asymmetry in brightness in the ring can be explained in terms of relativistic beaming of the emission from a plasma rotating close to the speed of light around a black hole. We compare our images to an extensive library of ray-traced general-relativistic magnetohydrodynamic simulations of black holes and derive a central mass of M = (6.5 ± 0.7) × 109
M
⊙. Our radio-wave observations thus provide powerful evidence for the presence of supermassive black holes in centers of galaxies and as the central engines of active galactic nuclei. They also present a new tool to explore gravity in its most extreme limit and on a mass scale that was so far not accessible.