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Letters to Nature

Nature 425, 934-937 (30 October 2003) | doi:10.1038/nature02065; Received 13 July 2003; Accepted 23 September 2003

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Near-infrared flares from accreting gas around the supermassive black hole at the Galactic Centre

R. Genzel1,2, R. Schödel1, T. Ott1, A. Eckart3, T. Alexander4, F. Lacombe5, D. Rouan5 & B. Aschenbach1

  1. Max-Planck-Institut für extraterrestrische Physik, Giessenbachstr. 1, 85748 Garching, Germany
  2. Department of Physics, Le Conte Hall, University of California, Berkeley, California 94720, USA
  3. I. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, 50937 Köln, Germany
  4. Faculty of Physics, The Weizmann Institute of Science, PO Box 26, Rehovot 76100, Israel
  5. Observatoire de Paris — Section de Meudon, 5 Place Jules Janssen, 92195 Meudon Cédex, France

Correspondence to: R. Genzel1,2 Email: genzel@mpe-garching.mpg.de

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Recent measurements of stellar orbits1, 2, 3 provide compelling evidence that the compact radio source Sagittarius A* (refs 4, 5) at the Galactic Centre is a 3.6-million-solar-mass black hole. Sgr A* is remarkably faint in all wavebands other than the radio region6, 7, however, which challenges current theories of matter accretion and radiation surrounding black holes8. The black hole's rotation rate is not known, and therefore neither is the structure of space-time around it. Here we report high-resolution infrared observations of Sgr A* that reveal 'quiescent' emission and several flares. The infrared emission originates from within a few milliarcseconds of the black hole, and traces very energetic electrons or moderately hot gas within the innermost accretion region. Two flares exhibit a 17-minute quasi-periodic variability. If the periodicity arises from relativistic modulation of orbiting gas, the emission must come from just outside the event horizon, and the black hole must be rotating at about half of the maximum possible rate.

  1. Max-Planck-Institut für extraterrestrische Physik, Giessenbachstr. 1, 85748 Garching, Germany
  2. Department of Physics, Le Conte Hall, University of California, Berkeley, California 94720, USA
  3. I. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, 50937 Köln, Germany
  4. Faculty of Physics, The Weizmann Institute of Science, PO Box 26, Rehovot 76100, Israel
  5. Observatoire de Paris — Section de Meudon, 5 Place Jules Janssen, 92195 Meudon Cédex, France

Correspondence to: R. Genzel1,2 Email: genzel@mpe-garching.mpg.de