First Sagittarius A* Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole in the Center of the Milky Way

Abstract

Abstract We present the first Event Horizon Telescope (EHT) observations of Sagittarius A* (Sgr A*), the Galactic center source associated with a supermassive black hole. These observations were conducted in 2017 using a global interferometric array of eight telescopes operating at a wavelength of λ = 1.3 mm. The EHT data resolve a compact emission region with intrahour variability. A variety of imaging and modeling analyses all support an image that is dominated by a bright, thick ring with a diameter of 51.8 ± 2.3 μ as (68% credible interval). The ring has modest azimuthal brightness asymmetry and a comparatively dim interior. Using a large suite of numerical simulations, we demonstrate that the EHT images of Sgr A* are consistent with the expected appearance of a Kerr black hole with mass ∼4 × 10 6 M ⊙ , which is inferred to exist at this location based on previous infrared observations of individual stellar orbits, as well as maser proper-motion studies. Our model comparisons disfavor scenarios where the black hole is viewed at high inclination ( i > 50°), as well as nonspinning black holes and those with retrograde accretion disks. Our results provide direct evidence for the presence of a supermassive black hole at the center of the Milky Way, and for the first time we connect the predictions from dynamical measurements of stellar orbits on scales of 10 3 –10 5 gravitational radii to event-horizon-scale images and variability. Furthermore, a comparison with the EHT results for the supermassive black hole M87* shows consistency with the predictions of general relativity spanning over three orders of magnitude in central mass.

Keywords

Affiliated Institutions

• Université Paris Cité FR
• Harvard University US
• Istituto Nazionale di Fisica Nucleare, Sezione di Cagliari IT
• University of Southern Denmark DK
• Institute of Astronomy and Astrophysics, Academia Sinica TW
• Osservatorio Astronomico di Cagliari IT
• University of Cagliari IT
• Sorbonne Université FR
• Yale University US
• California Institute of Technology US
• Rhodes University ZA
• Universitat de València ES
• Netherlands Institute for Radio Astronomy NL
• National Institute of Astrophysics, Optics and Electronics MX
• University of Groningen NL
• Fermi National Accelerator Laboratory US
• Parc Científic de la Universitat de València ES
• Centre National de la Recherche Scientifique FR
• Perimeter Institute CA
• University of Illinois Urbana-Champaign US
• Chinese Academy of Sciences CN
• University of Arizona US
• East Asian Observatory US
• Massachusetts Institute of Technology US
• Columbia University US
• McGill University CA
• Albert Einstein College of Medicine US
• University of California, Santa Barbara US
• Cornell University US
• The University of Texas at San Antonio US
• Woodwell Climate Research Center US
• Université Paris Sciences et Lettres FR
• University of Malaya MY
• Google (United States) US
• Goethe University Frankfurt DE
• University of Würzburg DE
• Fairfield University US
• Instituto de Astrofísica de Andalucía ES
• Institut de Radioastronomie Millimétrique FR
• National Radio Astronomy Observatory US
• University of the Witwatersrand ZA
• National Center for Supercomputing Applications US
• University of Hawaiʻi at Mānoa US
• Flatiron Health (United States) US
• Chalmers University of Technology SE
• Applied Mathematics (United States) US
• Secretaría de Ciencia, Humanidades, Tecnología e Innovación MX
• Atmospheric and Space Technology Research Associates (United States) US
• Korea University of Science and Technology KR
• University of Colorado Boulder US
• Leiden University NL
• Kavli Institute for the Physics and Mathematics of the Universe JP
• Center for Astrophysics Harvard & Smithsonian US
• University of Chicago US
• University of Massachusetts Amherst US
• Flatiron Institute
• University of Waterloo CA
• Las Cumbres Observatory Global Telescope Network US
• National Astronomical Observatories CN
• University of Pretoria ZA
• Korea Astronomy and Space Science Institute KR
• Laboratoire d’études spatiales et d’instrumentation en astrophysique FR
• Princeton University US
• Max Planck Institute for Radio Astronomy DE
• Observatoire de Paris FR
• The Graduate University for Advanced Studies, SOKENDAI JP
• AstroTec Holding (Netherlands) NL
• Istituto Nazionale di Fisica Nucleare, Sezione di Napoli IT
• The Institute of Statistical Mathematics JP
• The University of Tokyo JP
• Joint Institute for Laboratory Astrophysics US
• National Astronomical Observatory of Japan JP
• Université Bourgogne Franche-Comté FR
• Radboud University Nijmegen NL
• Whale Center of New England US

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