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                           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.   
      
                                   2025 August 4   
      The Andromeda Galaxy is shown just right of center, while some unusual   
         blue arcs appear to its left. Please see the explanation for more   
                               detailed information.   
      
                            Blue Arcs Toward Andromeda   
                       Image Credit & Copyright: Ogle et al.   
      
      Explanation: What are these gigantic blue arcs near the Andromeda   
      Galaxy (M31)? Discovered in 2022 by amateur astronomers, the faint arcs   
      -- dubbed SDSO 1 -- span nearly the same angular size as M31 itself. At   
      first, their origin was a mystery: are they actually near the Andromeda   
      Galaxy, or alternatively near to our Sun? Now, over 550 hours of   
      combined exposure and a collaboration between amateur and professional   
      astronomers has revealed strong evidence for their true nature: SDSO 1   
      is not intergalactic, but a new class of planetary nebula within our   
      galaxy. Dubbed a Ghost Planetary Nebula (GPN), SDSO 1 is the first   
      recognized member of a new subclass of faded planetary nebulas, along   
      with seven others also recently identified. Shown in blue are extremely   
      faint oxygen emission from the shock waves, while the surrounding red   
      is a hydrogen-emitting trail that indicates the GPN's age.   
      
                    Tomorrow's picture: complex stellar jumble   
        __________________________________________________________________   
      
          Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)   
               NASA Official: Amber Straughn Specific rights apply.   
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