                        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.

                                2026 July 18

                             Shadow and Rainbow
                   Image Credit & License: Dave Loschiavo

   Explanation: At sunset, an alignment of rainbow and mountain shadow was
   captured in this remarkable snapshot. The stunning view was recorded
   from a fire lookout on Smith Peak in the Plumas National Forest near
   Portola, California on July 13. Still, near sunset it's no accident
   that the majestic mountain shadow seems to point to the center of the
   graceful rainbow arc. Due to perspective and the long line of sight the
   mountain shadow naturally forms a tapering triangular shape, its apex
   positioned at the point opposite the Sun on the horizon. Following
   thunderstorms across the region, the rainbow arcs across the early
   evening sky, with its colorful and characteristic 42 degree arc formed
   as sunlight is refracted and reflected by the atmospheric water
   droplets. The geometric center of a rainbow arc lies at the antisolar
   point. And in this scene from the golden hour on planet Earth, that's
   also oposite the setting Sun along the distant horizon.

                   Tomorrow's picture: it came from space
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Amber Straughn Specific rights apply.
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                           NASA Science Activation
                             & Michigan Tech. U.

