Sagittarius A* (SgrA*) Black hole


  • Scientists from the Event Horizon Telescope (EHT) facility, at press conferences held simultaneously at several centres around the world, revealed the first image of the black hole at the centre of the Milky Way.

About Sagittarius A

  • The image of Sagittarius A* (SgrA*) gave further support to the idea that the compact object at the centre of our galaxy is indeed a black hole, strengthening Einstein’s general theory of relativity.

    Sagittarius A* (SgrA*) Black hole
    Credit: Wikipedia
  • In 2019, the Event Horizon Telescope facility, a collaboration of over 300 researchers, made history by releasing the first-ever image of a black hole, M87* — the black hole at the centre of Messier 87, a supergiant elliptic galaxy.
  • The ring-shaped image of SgrA*, which looked a lot similar to the one of M87*, occupied 52 microarcseconds in the field of view, which is as big a span of our view as a doughnut on the moon.
  • Sagittarius A* is 27,000 light years from us. At the press conference, the researchers said that imaging Sagittarius A* (SgrA*) was much more difficult than imaging M87*:
    • first, SgrA* is only one-thousandth the size of M87*;
    • second, the line of sight is obscured by a lot of matter; and as SgrA* is much smaller than M87*, the gas swirling around it takes only minutes to complete an orbit around SgrA* as opposed to taking weeks to go around M87*.
    • The last gives a variability that makes it difficult to image. A clear imaging requires long exposure of eight to 10 hours, where ideally the object should not change much.


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