                        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 w
                    ritten by a professional astronomer.

                               2021 November 9

                All of These Space Images are Fake Except One
             Image Credit: M. J. Smith et al. (U. Hertfordshire)

   Explanation: Why would you want to fake a universe? For one reason --
   to better understand our real universe. Many astronomical projects
   seeking to learn properties of our universe now start with a robotic
   telescope taking sequential images of the night sky. Next,
   sophisticated computer algorithms crunch these digital images to find
   stars and galaxies and measure their properties. To calibrate these
   algorithms, it is useful to test them on fake images from a fake
   universe to see if the algorithms can correctly deduce purposely
   imprinted properties. The featured mosaic of fake images was created to
   specifically mimic the images that have appeared on NASA's Astronomy
   Picture of the Day (APOD). Only one image of the 225 images is real --
   can you find it? The accomplished deceptors have made available
   individual fake APOD images that can be displayed by accessing their
   ThisIsNotAnAPOD webpage or Twitter feed. More useful for calibrating
   and understanding our distant universe, however, are fake galaxies -- a
   sampling of which can be seen at their ThisIsNotAGalaxy webpage.

    Astrophysicists: Browse 2,600+ codes in the Astrophysics Source Code
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                     Tomorrow's picture: gone in a flash
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Phillip Newman Specific rights apply.
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                      A service of: ASD at NASA / GSFC
                             & Michigan Tech. U.

