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 31
   [2]A starfield filled with a diffuse red glow has an unusual nebula on
   the lower left. The nebula has bright red filaments that curve down and
      appear to be reminiscent of a waterfall on Earth. Please see the
                 explanation for more detailed information.

                        HH-222: The Waterfall Nebula
                   Image Credit & Copyright: [3]Mike Selby

   Explanation: What created the Waterfall Nebula? The origin is still
   being researched. The structure, officially designated [4]Herbig-Haro
   222, appears in the region of [5]NGC 1999 in the [6]Great Orion
   Molecular Cloud complex. The elongated gaseous stream stretches about
   ten [7]light years but appears similar to a long [8]waterfall on Earth.
   [9]Recent observations indicate that [10]HH-222 is likely a gigantic
   gaseous [11]bow shock, similar to a [12]wave of water caused by a
   fast-moving ship. The origin of this [13]shock wave is thought to be a
   [14]jet outflow from the multiple [15]star system [16]V380 Orionis off
   the lower left of the frame. Therefore, gas [17]does not flow along the
   waterfall, but rather the entire structure moves toward the upper
   right. The [18]Waterfall Nebula lies about 1,500 [19]light years away
   toward the [20]constellation of Orion. The [21]featured image was
   captured earlier this month from [22]El Sauce Observatory in [23]Chile.

               Jigsaw Nebula: [24]Astronomy Puzzle of the Day
                       Tomorrow's picture: open space
     __________________________________________________________________

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    Authors & editors: [36]Robert Nemiroff ([37]MTU) & [38]Jerry Bonnell
                                 ([39]UMCP)
          NASA Official: Amber Straughn [40]Specific rights apply.
            [41]NASA Web Privacy, [42]Accessibility, [43]Notices;
                A service of: [44]ASD at [45]NASA / [46]GSFC,
                         [47]NASA Science Activation
                           & [48]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2512/WaterfallNeb_Selby_4000.jpg
   3. https://throughlightandtime.com/about/
   4. https://en.wikipedia.org/wiki/Herbig–Haro_object
   5. https://apod.nasa.gov/apod/ap180307.html
   6. https://apod.nasa.gov/apod/ap070125.html
   7. https://spaceplace.nasa.gov/light-year/
   8. https://apod.nasa.gov/apod/ap190112.html
   9. https://ui.adsabs.harvard.edu/abs/2013AJ....146..118R/abstract
  10. https://www.astroexplorer.org/details/aj481802f1
  11. https://en.wikipedia.org/wiki/Bow_shock
  12. https://youtu.be/95sQcSulRFM
  13. https://www.grc.nasa.gov/www/k-12/VirtualAero/BottleRocket/airplane/shock.html
  14. https://apod.nasa.gov/apod/ap250528.html
  15. https://science.nasa.gov/universe/stars/
  16. https://en.wikipedia.org/wiki/V380_Orionis
  17. https://media.istockphoto.com/id/1128004359/photo/close-up-scottish-fold-cat-head-with-shocking-face-and-wide-open-eyes-frighten-or-surprised.jpg?s=612x612&w=0&k=20&c=HglQ8Nf1PslTuI91T-dfhkln-iEbchjqfhGKCWTbaxg=
  18. https://en.wikipedia.org/wiki/HH_222
  19. https://science.nasa.gov/exoplanets/what-is-a-light-year/
  20. https://spaceplace.nasa.gov/constellations/
  21. https://throughlightandtime.com/hh-222-ha-rgb-rev-3-cdk-1000-26-dec-2025/
  22. https://youtu.be/shbwtlPIDI4
  23. https://en.wikipedia.org/wiki/Chile
  24. https://www.scigames.org/apps/webjigsaw2/index.php
  25. https://apod.nasa.gov/apod/ap251230.html
  26. https://apod.nasa.gov/apod/archivepix.html
  27. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  28. https://apod.nasa.gov/apod/lib/aptree.html
  29. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  30. https://apod.nasa.gov/apod/calendar/allyears.html
  31. https://apod.com/feed.rss
  32. https://apod.nasa.gov/apod/lib/edlinks.html
  33. https://apod.nasa.gov/apod/lib/about_apod.html
  34. https://asterisk.apod.com/discuss_apod.php?date=251231
  35. https://apod.nasa.gov/apod/ap260101.html
  36. http://www.phy.mtu.edu/faculty/Nemiroff.html
  37. http://www.phy.mtu.edu/
  38. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  39. http://www.astro.umd.edu/
  40. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  41. https://www.nasa.gov/about/highlights/HP_Privacy.html
  42. https://www.nasa.gov/general/accessibility/
  43. https://www.nasa.gov/privacy/
  44. https://astrophysics.gsfc.nasa.gov/
  45. https://www.nasa.gov/
  46. https://www.nasa.gov/centers/goddard/
  47. https://science.nasa.gov/learners
  48. http://www.mtu.edu/