                        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.

                              2024 February 12
   The image shows a dark field filled with stars and a diffuse red nebula
   running across horizontally. In the field are two circular objects that
   are bright, light colored. The lower object is larger and encircled in
   a blue glow. Please see the explanation for more detailed information.

                      HFG1 & Abell 6: Planetary Nebulae
   Image Credit & Copyright: Julien Cadena & Mickael Coulon; Text: Natalia
                          Lewandowska (SUNY Oswego)

   Explanation: Planetary nebulae like Heckathorn-Fesen-Gull 1 (HFG1) and
   Abell 6 in the constellation Cassiopeia are remnants from the last
   phase of a medium sized star like our Sun. In spite of their shapes,
   planetary nebulae have nothing in common with actual planets. Located
   in the bottom left part of the featured photo, HFG1 was created by the
   binary star system V664 Cas, which consists of a white dwarf star and a
   red giant star. Both stars orbit their center of mass over about half
   an Earth day. Traveling with the entire nebula at a speed about 300
   times faster than the fastest train on Earth, V664 Cas generates a
   bluish arc shaped shock wave. The wave interacts most strongly with the
   surrounding interstellar medium in the areas where the arc is
   brightest. After roughly 10,000 years, planetary nebulae become
   invisible due to a lack of ultraviolet light being emitted by the stars
   that create them. Displaying beautiful shapes and structures, planetary
   nebulae are highly desired objects for astrophotographers.

                       Tomorrow's picture: a wolf moon
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Amber Straughn; Specific rights apply.
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