                        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.

                               2021 October 5

                          Sunrise at the South Pole
   Image Credit & Copyright: Martin Wolf (U. Wisconsin), IceCube Neutrino
                         Obs., NSF; ht: Alice Allen

   Explanation: Sunrise at the South Pole is different. Usually a welcome
   sight, it follows months of darkness -- and begins months of sunshine.
   At Earth's poles, it can take weeks for the Sun to rise, in contrast
   with just minutes at any mid-latitude location. Sunrise at a pole is
   caused by the tilt of the Earth as it orbits the Sun, not by the
   rotation of the Earth. Although at a pole, an airless Earth would first
   see first Sun at an equinox, the lensing effect of the Earth's
   atmosphere and the size of the solar disk causes the top of the Sun to
   appear about two-weeks early. Pictured two weeks ago, the Sun peaks
   above the horizon of a vast frozen landscape at Earth's South Pole. The
   true South Pole is just a few meters to the left of the communications
   tower. This polar sunrise capture was particularly photogenic as the
   Sun appeared capped by a green flash.

                     Tomorrow's picture: streaming orion
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