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.

                                2021 July 25
    [2]The picture shows the planet Neptune and its moon Triton, both in
     crescent phases, as captured by the passing Voyager 2 spacecraft in
       1989. Please see the explanation for more detailed information.

                         Crescent Neptune and Triton
                     Image Credit: [3]NASA, [4]Voyager 2

   Explanation: Gliding silently through the outer [5]Solar System, the
   [6]Voyager 2 spacecraft camera captured [7]Neptune and [8]Triton
   together in crescent phase. The [9]elegant picture of the [10]gas giant
   planet and its [11]cloudy moon was taken from behind just after
   [12]closest approach in 1989. It could not have been taken from
   [13]Earth because [14]Neptune never shows a crescent phase to sunward
   Earth. The [15]unusual vantage point also robs [16]Neptune of its
   familiar [17]blue hue, as sunlight seen from here is scattered forward,
   and so is reddened like the [18]setting Sun. [19]Neptune is smaller but
   more massive than [20]Uranus, has several [21]dark rings, and [22]emits
   more light than it receives from the Sun.

                     Tomorrow's picture: galaxy grabber
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    Authors & editors: [34]Robert Nemiroff ([35]MTU) & [36]Jerry Bonnell
                                 ([37]UMCP)
          NASA Official: Phillip Newman [38]Specific rights apply.
              [39]NASA Web Privacy Policy and Important Notices
                A service of: [40]ASD at [41]NASA / [42]GSFC
                           & [43]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2107/neptunetriton_voyager_960.jpg
   3. https://www.nasa.gov/
   4. https://voyager.jpl.nasa.gov/
   5. https://solarsystem.nasa.gov/solar-system/our-solar-system/overview/
   6. https://www.jpl.nasa.gov/missions/voyager-2
   7. http://en.wikipedia.org/wiki/Neptune
   8. https://apod.nasa.gov/apod/ap070304.html
   9. http://pds.jpl.nasa.gov/planets/captions/neptune/parting.htm
  10. https://solarsystem.nasa.gov/planets/neptune/in-depth/
  11. https://en.wikipedia.org/wiki/Triton_(moon)#Atmosphere
  12. https://apod.nasa.gov/apod/ap140826.html
  13. https://apod.nasa.gov/apod/ap070325.html
  14. https://youtu.be/NStn7zZKXfE
  15. https://photojournal.jpl.nasa.gov/catalog/PIA02247
  16. https://open.spotify.com/episode/5Hc4tnazxSYJZdltUW0IV2
  17. https://apod.nasa.gov/apod/ap150215.html
  18. https://apod.nasa.gov/apod/ap151202.html
  19. https://nssdc.gsfc.nasa.gov/photo_gallery/photogallery-neptune.html
  20. https://en.wikipedia.org/wiki/Uranus
  21. http://pds-rings.seti.org/neptune/
  22. https://en.wikipedia.org/wiki/Neptune#Internal_heating
  23. https://apod.nasa.gov/apod/ap210724.html
  24. https://apod.nasa.gov/apod/archivepix.html
  25. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  26. https://apod.nasa.gov/apod/lib/aptree.html
  27. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  28. https://apod.nasa.gov/apod/calendar/allyears.html
  29. https://apod.nasa.gov/apod.rss
  30. https://apod.nasa.gov/apod/lib/edlinks.html
  31. https://apod.nasa.gov/apod/lib/about_apod.html
  32. http://asterisk.apod.com/discuss_apod.php?date=210725
  33. https://apod.nasa.gov/apod/ap210726.html
  34. http://www.phy.mtu.edu/faculty/Nemiroff.html
  35. http://www.phy.mtu.edu/
  36. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  37. http://www.astro.umd.edu/
  38. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  39. https://www.nasa.gov/about/highlights/HP_Privacy.html
  40. https://astrophysics.gsfc.nasa.gov/
  41. https://www.nasa.gov/
  42. https://www.nasa.gov/centers/goddard/
  43. http://www.mtu.edu/