                        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 March 20

                     Spring Equinox at Teide Observatory
      Image Credit & Copyright: Juan Carlos Casado (Starry Earth, TWAN)

   Explanation: The defining astronomical moment of the equinox today is
   at 14:46 UTC (March 20). That's when the Sun crosses the celestial
   equator moving north in its yearly journey through planet Earth's sky,
   marking the beginning of spring for our fair planet in the northern
   hemisphere and fall in the southern hemisphere. Then, day and night are
   nearly equal around the globe. In fact, both day and nighttime
   exposures from a spring equinox at the Observatorio del Teide in
   Tenerife, Canary Islands, Spain, are used in this composited skyscape.
   Over 1,000 images were taken with a fisheye lens and merged in the
   ambitious equinox project. The apparent motion of the Sun setting along
   the celestial equator on the equinox date follows the bright linear,
   diagonal track from the sequence of daytime exposures taken over 6
   hours. After sunset, nighttime exposures recorded startrails, with the
   celestial equator as a linear track and concentric arcs circling the
   north celestial pole near Polaris at upper right and the south
   celestial pole beyond the lower left edge (and below the Teide
   horizon). The foreground includes the distant Teide volcano peak and
   the observatory's pyramid-shaped solar laboratory building.

                  Tomorrow's picture: NGC 1300 and Friends
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
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