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.

                               2019 October 11

                          Planet Earth at Blue Hour
                 Image Credit & Copyright: Matthias Ciprian

   Explanation: Nature photographers and other fans of planet Earth always
   look forward to the blue hour. That's the transition in twilight, just
   before sunrise or after sunset, when the Sun is below the horizon but
   land and sky are still suffused with beautiful bluish hues of light. On
   August 8 this early morning blue hour panorama scanned along the clear
   western sky, away from the impending sunrise. A breathtaking scene, it
   looks down the slopes of Mt. Whitney, from along the John Muir Trail
   toward rugged peaks of planet Earth's Sierra Nevada mountain range.
   Above the horizon a faint pinkish band of back scattered sunlight, the
   anti-twilight arch or Belt of Venus, borders the falling grey shadow of
   Earth itself. Subtle bands of light across the clear sky are
   anti-crepuscular rays, defined by shadows of clouds near the sunward
   horizon. Actually following parallel lines they seem to converge along
   the horizon at the point opposite the rising Sun due to perspective.

                      Tomorrow's picture: light-weekend
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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.

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