Subj : Daily APOD Report
To   : All
From : Alan Ianson
Date : Mon Aug 23 2021 08:18:56

                        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.

                               2021 August 23

               Abell 3827: Cannibal Cluster Gravitational Lens
                 Image Credit: ESA/Hubble & NASA, R. Massey

   Explanation: Is that one galaxy or three? Toward the right of the
   featured Hubble image of the massive galaxy cluster Abell 3827 is what
   appears to be a most unusual galaxy -- curved and with three centers. A
   detailed analysis, however, finds that these are three images of the
   same background galaxy -- and that there are at least four more images.
   Light we see from the single background blue galaxy takes multiple
   paths through the complex gravity of the cluster, just like a single
   distant light can take multiple paths through the stem of a wine glass.
   Studying how clusters like Abell 3827 and their component galaxies
   deflect distant light gives information about how mass and dark matter
   are distributed. Abell 3827 is so distant, having a redshift of 0.1,
   that the light we see from it left about 1.3 billion years ago --
   before dinosaurs roamed the Earth. Therefore, the cluster's central
   galaxies have now surely all coalesced -- in a feast of galactic
   cannibalism -- into one huge galaxy near the cluster's center.

                Tomorrow's picture: planet-forming space disk
     __________________________________________________________________

       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Phillip Newman Specific rights apply.
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                             & Michigan Tech. U.

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