Astronomy Picture of the Day

   [1]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.

                              2025 December 21
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                        Solstice on a Spinning Earth
    Image Credit: [2]Meteosat 9, [3]NASA, [4]Earth Observatory, [5]Robert
                                   Simmon

   Explanation: Can you tell that today is a solstice by the tilt of the
   Earth? Yes. At a solstice, the [6]Earth's terminator -- the dividing
   line between night and day -- is tilted the most. The [7]featured
   time-lapse video demonstrates this by displaying an entire year on
   [8]planet Earth in twelve seconds. From [9]geosynchronous orbit, the
   [10]Meteosat 9 satellite recorded [11]infrared images of the Earth
   every day at the same [12]local time. The video started at the
   [13]September 2010 equinox with the terminator line being vertical: an
   equinox. As the [14]Earth revolved around the Sun, the terminator was
   seen to tilt in a way that provides less daily sunlight to the northern
   hemisphere, [15]causing winter in the north. At the [16]most tilt,
   winter solstice occurred [17]in the north, and summer [18]solstice in
   the south. As the year progressed, the [19]March 2011 equinox arrived
   halfway through the video, followed by the terminator [20]tilting the
   other way, [21]causing winter in the southern hemisphere -- and summer
   in the north. The captured year ends again with the [22]September
   equinox, concluding another of the billions of trips the Earth has
   taken -- and will take -- around the Sun.

              APOD Review: [23]RJN's Night Sky Network Lecture
                    Tomorrow's picture: strange lightning
     __________________________________________________________________

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    Authors & editors: [35]Robert Nemiroff ([36]MTU) & [37]Jerry Bonnell
                                 ([38]UMCP)
          NASA Official: Amber Straughn [39]Specific rights apply.
            [40]NASA Web Privacy, [41]Accessibility, [42]Notices;
                A service of: [43]ASD at [44]NASA / [45]GSFC,
                         [46]NASA Science Activation
                           & [47]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://www.eumetsat.int/our-satellites/meteosat-series
   3. https://www.nasa.gov/
   4. https://earthobservatory.nasa.gov/
   5. https://www.nasa.gov/centers/goddard/about/people/RSimmon.html
   6. https://en.wikipedia.org/wiki/Terminator_(solar)
   7. https://www.youtube.com/watch?v=LUW51lvIFjg
   8. https://spaceplace.nasa.gov/all-about-earth/
   9. https://en.wikipedia.org/wiki/Geosynchronous_orbit
  10. https://en.wikipedia.org/wiki/Meteosat
  11. https://science.nasa.gov/ems/07_infraredwaves/
  12. http://time.gov/
  13. http://apod.nasa.gov/apod/calendar/ca1009.html
  14. https://science.nasa.gov/earth/
  15. https://spaceplace.nasa.gov/seasons/
  16. https://www.reddit.com/media?url=https://external-preview.redd.it/21AJtS8T1bwvpyZPzjD9iOMijuFVaovzIVlNB2EZPJg.jpg?auto=webp&s=7f69f67d6aa77074bcd4e33ebaa47d79dc152b1e
  17. https://science.nasa.gov/kids/earth/which-pole-is-colder/
  18. https://en.wikipedia.org/wiki/Solstice
  19. http://apod.nasa.gov/apod/calendar/ca1103.html
  20. https://media3.giphy.com/media/JOe1P4jUAhTKhPI787/giphy.gif
  21. http://www.universetoday.com/75843/why-are-there-seasons/
  22. https://apod.nasa.gov/apod/ap220321.html
  23. https://www.youtube.com/watch?v=_txUmGTtBhQ
  24. https://apod.nasa.gov/apod/ap251220.html
  25. https://apod.nasa.gov/apod/archivepix.html
  26. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  27. https://apod.nasa.gov/apod/lib/aptree.html
  28. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  29. https://apod.nasa.gov/apod/calendar/allyears.html
  30. https://apod.com/feed.rss
  31. https://apod.nasa.gov/apod/lib/edlinks.html
  32. https://apod.nasa.gov/apod/lib/about_apod.html
  33. https://asterisk.apod.com/discuss_apod.php?date=251221
  34. https://apod.nasa.gov/apod/ap251222.html
  35. http://www.phy.mtu.edu/faculty/Nemiroff.html
  36. http://www.phy.mtu.edu/
  37. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  38. http://www.astro.umd.edu/
  39. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  40. https://www.nasa.gov/about/highlights/HP_Privacy.html
  41. https://www.nasa.gov/general/accessibility/
  42. https://www.nasa.gov/privacy/
  43. https://astrophysics.gsfc.nasa.gov/
  44. https://www.nasa.gov/
  45. https://www.nasa.gov/centers/goddard/
  46. https://science.nasa.gov/learners
  47. http://www.mtu.edu/