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.

                                2019 March 20
                           Equinox on Planet Earth
          Image Credit: NASA [2] , Meteosat [3] , Robert Simmon [4]

Explanation: Welcome to an equinox [5]  on planet Earth. Today is the first
day of spring in our fair planet's northern hemisphere, fall in the southern
hemisphere, with day and night nearly equal around the globe. At an equinox
Earth's terminator [6] , the dividing line between day and night, connects the
planet's north and south poles as seen at the start of this remarkable
time-lapse video [7]  compressing an entire year into twelve seconds. To make
it, the Meteosat [8]  satellite recorded these infrared images [9]  every day
at the same local time from a geosynchronous orbit. The video actually starts
at the September 2010 equinox with the terminator aligned vertically. As the
Earth revolves [10] around the Sun, the terminator [11]  tilts to provide less
daily sunlight to the northern hemisphere, reaching the solstice and northern
hemisphere winter at the maximum tilt. As the year continues, the terminator
tilts back again and March 2011 equinox arrives halfway through the video.
Then the terminator swings past vertical the other way, reaching the the June
2011 solstice and the beginning of [12]  northern summer. The video ends as
the September equinox [13]  returns.

               Tomorrow's picture: a northern seasonal symphony

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    Authors & editors: Robert Nemiroff [25] (MTU [26] ) & Jerry Bonnell [27]
                                  (UMCP [28] )
          NASA Official:  Phillip Newman Specific rights apply [29] .
              NASA Web Privacy Policy and Important Notices [30]
              A service of: ASD [31]  at NASA [32]  / GSFC [33]
                           & Michigan Tech. U. [34]
----------
Site notes:
  [1] archivepix.html
  [2] https://www.nasa.gov/
  [3]
http://www.eumetsat.int/website/home/Satellit...
index.html
  [4] https://www.nasa.gov/centers/goddard/about/pe...
  [5] http://en.wikipedia.org/wiki/Equinox
  [6] http://en.wikipedia.org/wiki/Terminator_(sola...
  [7] http://www.youtube.com/watch?v=LUW51lvIFjg
  [8] http://en.wikipedia.org/wiki/Meteosat
  [9] http://earthobservatory.nasa.gov/IOTD/view.ph...
  [10] http://www.youtube.com/watch?v=q4_-R1vnJyw
  [11] ap130406.html
  [12] http://en.wikipedia.org/wiki/ Seasons#Causes_and_effects
  [13] ap120923.html
  [14] ap190319.html
  [15] archivepix.html
  [16] lib/apsubmit2015.html
  [17] lib/aptree.html
  [18] https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apo...
  [19] calendar/allyears.html
  [20] /apod.rss
  [21] lib/edlinks.html
  [22] lib/about_apod.html
  [23] http://asterisk.apod.com/discuss_apod.php?dat...
  [24] ap170321.html
  [25] http://www.phy.mtu.edu/faculty/Nemiroff.html
  [26] http://www.phy.mtu.edu/
  [27] https://antwrp.gsfc.nasa.gov/htmltest/jbonnel...
  [28] http://www.astro.umd.edu/
  [29] lib/about_apod.html#srapply
  [30] https://www.nasa.gov/about/highlights/HP_Priv...
  [31] https://astrophysics.gsfc.nasa.gov/
  [32] https://www.nasa.gov/
  [33] https://www.nasa.gov/centers/goddard/
  [34] http://www.mtu.edu/

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