                        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.

                                2023 April 15

                             When Z is for Mars
                 Image Credit & Copyright: Tunc Tezel (TWAN)

   Explanation: A composite of images captured about a week apart from mid
   August 2022 through late March 2023, this series traces the retrograde
   motion of ruddy-colored Mars. Progressing from lower right to upper
   left Mars makes a Z-shaped path as it wanders past the Pleiades and
   Hyades star clusters, through the constellation Taurus in planet
   Earth's night sky. Seen about every two years, Mars doesn't actually
   reverse the direction of its orbit to trace out the Z-shape though.
   Instead, the apparent backwards or retrograde motion with respect to
   the background stars is a reflection of the orbital motion of Earth
   itself. Retrograde motion can be seen each time Earth overtakes and
   laps planets orbiting farther from the Sun, the Earth moving more
   rapidly through its own relatively close-in orbit. High in northern
   hemisphere skies the Red Planet was opposite the Sun and at its closest
   and brightest on December 8, near the center of the frame. Seen close
   to Mars, a popular visitor to the inner Solar System, comet ZTF (C/2022
   E3), was also captured on two dates, February 10 and February 16.

                       Tomorrow's picture: winging it
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Phillip Newman Specific rights apply.
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