                        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.

                               2024 January 13

                              Circling the Sun
                  Image Credit & Copyright: Radoslav Zboran

   Explanation: Earth's orbit around the Sun is not a circle, it's an
   ellipse. The point along its elliptical orbit where our fair planet is
   closest to the Sun is called perihelion. This year, perihelion was on
   January 2 at 01:00 UTC, with the Earth about 3 million miles closer to
   the Sun than it was at aphelion (last July 6), the farthest point in
   its elliptical orbit. Of course, distance from the Sun doesn't
   determine the seasons, and it doesn't the determine size of Sun halos.
   Easier to see with the Sun hidden behind a tall tree trunk, this
   beautiful ice halo forms a 22 degree-wide circle around the Sun,
   recorded while strolling through the countryside near Heroldstatt,
   Germany. The Sun halo's 22 degree angular diameter is determined by the
   six-sided geometry of water ice crystals drifting high in planet
   Earth's atmosphere.

                    Tomorrow's picture: there be dragons
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