                        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.

                               2023 October 4
      A colorful star field surrounds a big blue reflection nebula. The
   nebula is elongated across the wide frame and said to resemble the head
    of folklore-based witch. Please see the explanation for more detailed
                                information.

                       IC 2118: The Witch Head Nebula
                 Image Credit & Copyright: Abdullah Alharbi

   Explanation: Does this nebula look like the head of a witch? The nebula
   is known popularly as the Witch Head Nebula because, it is said, the
   nebula's shape resembles a Halloween-style caricature of a witch's
   head. Exactly how, though, can be a topic of imaginative speculation.
   What is clear is that IC 2118 is about 50 light-years across and made
   of gas and dust that points to -- because it has been partly eroded by
   -- the nearby star Rigel. One of the brighter stars in the
   constellation Orion, Rigel lies below the bottom of the featured image.
   The blue color of the Witch Head Nebula and is caused not only by
   Rigel's intense blue starlight but because the dust grains scatter blue
   light more efficiently than red. The same physical process causes
   Earth's daytime sky to appear blue, although the scatterers in planet
   Earth's atmosphere are molecules of nitrogen and oxygen.

                       Tomorrow's picture: open space
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