Astronomy Picture of the Day

                         Astronomy Picture of the Day

    Discover the cosmos! [1] Each day a different image or photograph of our
 fascinating universe is featured, along with a brief explanation written by a
                           professional astronomer.

                                2018 November 8
                                      [2]
                              Mars in the Loop
          Image Credit & Copyright [3] : Tunc Tezel [4] (TWAN [5] )

Explanation: This composite of images spaced some 5 to 9 days apart, from late
April (bottom right) through November 5 (top left), traces the retrograde
motion of ruddy-colored Mars [6]  through planet Earth's night sky [7] . To
connect the dots and dates in this 2018 Mars retrograde loop, just slide your
cursor over the picture (and check out this animation [8] ). But Mars didn't
actually reverse the direction of its orbit. Instead, the apparent backwards
motion with respect to the background stars is a reflection of the motion of
the Earth itself. Retrograde motion can be seen [9]  each time Earth overtakes
and laps planets orbiting farther from the Sun, the Earth moving more rapidly
through its own relatively close-in orbit. On July 27, Mars was near its
favorable 2018 parihelic opposition, when Mars was closest to the Sun in its
orbit while also opposite the Sun [10]  in Earth's sky. For that date, the
frame used in this composite was taken during the total lunar eclipse [11] .

                          Tomorrow's picture: lookout

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    Authors & editors: Robert Nemiroff [23] (MTU [24] ) & Jerry Bonnell [25]
                                  (UMCP [26] )
          NASA Official:  Phillip Newman Specific rights apply [27] .
              NASA Web Privacy Policy and Important Notices [28]
              A service of: ASD [29]  at NASA [30]  / GSFC [31]
                           & Michigan Tech. U. [32]
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Site notes:
  [1] archivepix.html
  [2] image/1811/Ma2018_tezelN.jpg
  [3] lib/about_apod.html#srapply
  [4] http://www.twanight.org/tezel
  [5] http://www.twanight.org/
  [6] https://mars.nasa.gov/
  [7] http://www.twanight.org/Mars
  [8] https://vimeo.com/298439756
  [9] http://projects.astro.illinois.edu/data/Retrograde/
  [10] ap180727.html
  [11] ap180802.html
  [12] ap181107.html
  [13] archivepix.html
  [14] lib/apsubmit2015.html
  [15] lib/aptree.html
  [16] https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  [17] calendar/allyears.html
  [18] /apod.rss
  [19] lib/edlinks.html
  [20] lib/about_apod.html
  [21] http://asterisk.apod.com/discuss_apod.php?date=181108
  [22] ap181109.html
  [23] http://www.phy.mtu.edu/faculty/Nemiroff.html
  [24] http://www.phy.mtu.edu/
  [25] https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  [26] http://www.astro.umd.edu/
  [27] lib/about_apod.html#srapply
  [28] https://www.nasa.gov/about/highlights/HP_Privacy.html
  [29] https://astrophysics.gsfc.nasa.gov/
  [30] https://www.nasa.gov/
  [31] https://www.nasa.gov/centers/goddard/
  [32] http://www.mtu.edu/

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