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.

                              2019 December 29
    [2]See Explanation. Clicking on the picture will download the highest
                        resolution version available.

               Cassini Spacecraft Crosses Saturn's Ring Plane
   Image Credit: [3]NASA, [4]ESA, [5]JPL, [6]ISS, [7]Cassini Imaging Team;
                     Processing: Fernando Garcia Navarro

   Explanation: If this is Saturn, where are the rings? When Saturn's
   "appendages" [8]disappeared in 1612, [9]Galileo did not understand why.
   Later that century, it became understood that [10]Saturn's unusual
   protrusions were rings and that when the [11]Earth crosses the ring
   plane, the edge-on rings will [12]appear to disappear. This is because
   Saturn's rings are confined to a [13]plane many times thinner, in
   proportion, than a [14]razor blade. In modern times, the [15]robot
   Cassini spacecraft orbiting Saturn frequently crossed [16]Saturn's ring
   plane during its mission to Saturn, from 2004 to 2017. A series of
   plane crossing images from 2005 February was dug out of the vast
   [17]online Cassini raw image archive by interested Spanish amateur
   Fernando Garcia Navarro. [18]Pictured here, digitally cropped and set
   in representative colors, is the striking result. [19]Saturn's thin
   ring plane appears in blue, bands and clouds in [20]Saturn's upper
   atmosphere appear in gold. Details of Saturn's rings can be seen in the
   high [21]dark shadows across the top of this image, taken back in 2005.
   The moons [22]Dione and [23]Enceladus appear as [24]bumps in the rings.

     Free Presentation: [25]APOD Editor to show best astronomy images of
                2019 -- and the decade -- in NYC on January 3
                   Tomorrow's picture: nebulae triple play
     __________________________________________________________________

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    Authors & editors: [37]Robert Nemiroff ([38]MTU) & [39]Jerry Bonnell
                                 ([40]UMCP)
          NASA Official: Phillip Newman [41]Specific rights apply.
              [42]NASA Web Privacy Policy and Important Notices
                A service of: [43]ASD at [44]NASA / [45]GSFC
                           & [46]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix2015.html
   2. https://apod.nasa.gov/apod/image/1912/saturnplane_cassini_1004.jpg
   3. https://www.nasa.gov/
   4. https://www.esa.int/
   5. https://www.jpl.nasa.gov/
   6. http://ciclops.org/iss/iss.php
   7. http://ciclops.org/
   8. https://science.nasa.gov/science-news/science-at-nasa/2008/18mar_saturn
   9. https://en.wikipedia.org/wiki/Galileo_Galilei
  10. https://solarsystem.nasa.gov/planets/saturn/overview/
  11. https://apod.nasa.gov/apod/ap950801.html
  12. http://www.youtube.com/watch?v=ZaTAYOpUP6o
  13. http://coolcosmos.ipac.caltech.edu/ask/108-How-large-are-Saturn-s-rings
  14. http://en.wikipedia.org/wiki/Razor
  15. https://solarsystem.nasa.gov/missions/cassini/mission/spacecraft/cassini-orbiter/
  16. https://apod.nasa.gov/apod/ap040117.html
  17. https://solarsystem.nasa.gov/raw-images/raw-image-viewer/
  18. http://www.slate.com/blogs/bad_astronomy/2005/05/31/saturn_sans_rings.html
  19. https://apod.nasa.gov/apod/ap080720.html
  20. https://apod.nasa.gov/apod/ap041102.html
  21. https://apod.nasa.gov/apod/ap090901.html
  22. https://apod.nasa.gov/apod/ap121105.html
  23. https://apod.nasa.gov/apod/ap180701.html
  24. http://asterisk.apod.com/viewtopic.php?f=9&t=18340&p=230228#p230227
  25. http://asterisk.apod.com/viewtopic.php?f=28&t=40052
  26. https://apod.nasa.gov/apod/ap191228.html
  27. https://apod.nasa.gov/apod/archivepix2015.html
  28. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  29. https://apod.nasa.gov/apod/lib/aptree.html
  30. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  31. https://apod.nasa.gov/apod/calendar/allyears.html
  32. https://apod.nasa.gov/apod.rss
  33. https://apod.nasa.gov/apod/lib/edlinks.html
  34. https://apod.nasa.gov/apod/lib/about_apod.html
  35. http://asterisk.apod.com/discuss_apod.php?date=191229
  36. https://apod.nasa.gov/apod/ap191230.html
  37. http://www.phy.mtu.edu/faculty/Nemiroff.html
  38. http://www.phy.mtu.edu/
  39. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  40. http://www.astro.umd.edu/
  41. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  42. https://www.nasa.gov/about/highlights/HP_Privacy.html
  43. https://astrophysics.gsfc.nasa.gov/
  44. https://www.nasa.gov/
  45. https://www.nasa.gov/centers/goddard/
  46. http://www.mtu.edu/