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2 results

  • 7 - The First Image of a Black Hole

  • Luciano Rezzolla, Goethe-Universität Frankfurt Am Main
  • Book:
    The Irresistible Attraction of Gravity
    Published online:
    02 March 2023
    Print publication:
    02 March 2023, pp 146-204

  • Summary

    This chapter explains how the researchers of the Event Horizon Telescope Collaboration were able to obtain the first picture of a black hole through radio-astronomical observations. In particular, we first describe the technological strategies that have been exploited in order to obtain a record-high angular resolution. We will also discuss the theoretical aspects that have allowed the collaboration to model the dynamics of the plasma falling onto the black and to produce a large database of synthetic images potentially describing an accreting supermassive black hole. The chapter reviews how the comparison between the theoretical images and the observations has allowed us to deduce the presence of a supermassive black hole with a mass of 6 billion solar masses in the very heart of the giant galaxy M87. The chapter will also summarise the lessons that have been learnt from this epochal achievement and the questions that are still left unanswered about black holes and gravity in the strongest regimes.

  • Extending the Observable Zenith Angle of FAST Using an Offset Feed

  • Li Guoding, R. Nan, B. Peng
  • Journal:
    International Astronomical Union Colloquium / Volume 182 / 2001
    Published online by Cambridge University Press:
    12 April 2016, pp. 255-259
    Print publication:
    2001
    • Article
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  • The five hundred meter aperture spherical radio telescope is will use an active spherical reflector. When the zenith scan angle is changed, the illuminated part of the reflecting surface is made to fit a paraboloid of revolution in real time by active control. The maximum zenith scan angle | ψmax | of FAST is 30° under conditions of the geometry selected in order that the feed does not illuminate the ground. The result of this paper shows that the maximum zenith scan angle | ψmax | can be extended to 69° by offsetting the feed.