                        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.

                               2020 August 30

                    NGC 6357: Cathedral to Massive Stars
         Image Credit: NASA, ESA and Jesús Maíz Apellániz (IAA, Spain);
               Acknowledgement: Davide De Martin (ESA/Hubble)

   Explanation: How massive can a normal star be? Estimates made from
   distance, brightness and standard solar models had given one star in
   the open cluster Pismis 24 over 200 times the mass of our Sun, making
   it one of the most massive stars known. This star is the brightest
   object located just above the gas front in the featured image. Close
   inspection of images taken with the Hubble Space Telescope, however,
   have shown that Pismis 24-1 derives its brilliant luminosity not from a
   single star but from three at least. Component stars would still remain
   near 100 solar masses, making them among the more massive stars
   currently on record. Toward the bottom of the image, stars are still
   forming in the associated emission nebula NGC 6357. Appearing perhaps
   like a Gothic cathedral, energetic stars near the center appear to be
   breaking out and illuminating a spectacular cocoon.

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