                        Astronomy Picture of the Day

    Discover the cosmos! Each day a different image or photograph of our
      fascinating universe is featured, along with a brief explanation
                    written by a professional astronomer.

                                 2022 May 1

                  First Horizon-Scale Image of a Black Hole
             Image Credit: Event Horizon Telescope Collaboration

   Explanation: What does a black hole look like? To find out, radio
   telescopes from around the Earth coordinated observations of black
   holes with the largest known event horizons on the sky. Alone, black
   holes are just black, but these monster attractors are known to be
   surrounded by glowing gas. This first image resolves the area around
   the black hole at the center of galaxy M87 on a scale below that
   expected for its event horizon. Pictured, the dark central region is
   not the event horizon, but rather the black hole's shadow -- the
   central region of emitting gas darkened by the central black hole's
   gravity. The size and shape of the shadow is determined by bright gas
   near the event horizon, by strong gravitational lensing deflections,
   and by the black hole's spin. In resolving this black hole's shadow,
   the Event Horizon Telescope (EHT) bolstered evidence that Einstein's
   gravity works even in extreme regions, and gave clear evidence that M87
   has a central spinning black hole of about 6 billion solar masses.
   Since releasing this featured image in 2019, the EHT has expanded to
   include more telescopes, observe more black holes, track polarized
   light,and is working to observe the immediately vicinity of the black
   hole in the center of our Milky Way Galaxy.

                        This week is: Black Hole Week
               New EHT Results to be Announced: Next Thursday
                       Tomorrow's picture: martian sun
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Phillip Newman Specific rights apply.
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                             & Michigan Tech. U.

