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.

                                2024 April 22
      [2]A dark mountain ridge is pictured across the foreground at the
   bottom. Smoke is rising about the ridge, and a close inspection reveals
    that some of this smoke form rings. The background has a reddish hue,
      and a crescent Moon is visible on the upper left. Please see the
                 explanation for more detailed information.

                     Moon and Smoke Rings from Mt. Etna
                Image Credit & Copyright: [3]Dario Giannobile

   Explanation: Yes, but can your volcano do this? To the [4]surprise of
   some, [5]Mt. Etna emits, on occasion, smoke rings. Technically known as
   [6]vortex rings, the walls of the volcano slightly slow the outside of
   [7]emitted smoke puffs, causing the inside gas to move faster. A circle
   of low pressure develops so that the emitted puff of [8]volcanic gas
   and [9]ash loops around in a [10]ring, a familiar geometric structure
   that can be surprisingly stable as it rises. [11]Smoke rings are quite
   rare and need a coincidence of the right [12]geometry of the vent, the
   right speed of [13]ejected smoke, and the relative calmness of the
   outside atmosphere. In the [14]featured image taken about two weeks ago
   from [15]Gangi, [16]Sicily, [17]Italy, multiple volcanic smoke rings
   are visible. The scene is shaded by the [18]red light of a dawn
   [19]Sun, while a [20]crescent Moon is visible in the background.

                          Tomorrow's picture: sky X
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    Authors & editors: [32]Robert Nemiroff ([33]MTU) & [34]Jerry Bonnell
                                 ([35]UMCP)
          NASA Official: Amber Straughn [36]Specific rights apply.
            [37]NASA Web Privacy, [38]Accessibility, [39]Notices;
                A service of: [40]ASD at [41]NASA / [42]GSFC,
                         [43]NASA Science Activation
                           & [44]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2404/EtnaRingsMoonCrop_Giannobile_960.jpg
   3. https://www.instagram.com/astro_dariogiannobile/
   4. 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=
   5. https://youtu.be/4ACzGDPnsAM?t=7
   6. https://en.wikipedia.org/wiki/Vortex_ring
   7. https://youtu.be/izlsxgAvL18
   8. https://en.wikipedia.org/wiki/Volcanic_gas
   9. https://en.wikipedia.org/wiki/Volcanic_ash
  10. https://apod.nasa.gov/apod/ap230814.html
  11. https://youtu.be/ckFdAVFgIR8
  12. https://youtu.be/N7d_RWyOv20
  13. https://apod.nasa.gov/apod/ap030102.html
  14. https://www.instagram.com/p/C5h7DueonwE/
  15. https://youtu.be/VNQVtyNQQ9A
  16. https://en.wikipedia.org/wiki/Sicily
  17. https://en.wikipedia.org/wiki/Italy
  18. https://apod.nasa.gov/apod/ap240228.html
  19. https://science.nasa.gov/sun/
  20. https://svs.gsfc.nasa.gov/5187/
  21. https://apod.nasa.gov/apod/ap240421.html
  22. https://apod.nasa.gov/apod/archivepix.html
  23. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  24. https://apod.nasa.gov/apod/lib/aptree.html
  25. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  26. https://apod.nasa.gov/apod/calendar/allyears.html
  27. https://apod.com/feed.rss
  28. https://apod.nasa.gov/apod/lib/edlinks.html
  29. https://apod.nasa.gov/apod/lib/about_apod.html
  30. https://asterisk.apod.com/discuss_apod.php?date=240422
  31. https://apod.nasa.gov/apod/ap240423.html
  32. http://www.phy.mtu.edu/faculty/Nemiroff.html
  33. http://www.phy.mtu.edu/
  34. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  35. http://www.astro.umd.edu/
  36. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  37. https://www.nasa.gov/about/highlights/HP_Privacy.html
  38. https://www.nasa.gov/general/accessibility/
  39. https://www.nasa.gov/privacy/
  40. https://astrophysics.gsfc.nasa.gov/
  41. https://www.nasa.gov/
  42. https://www.nasa.gov/centers/goddard/
  43. https://science.nasa.gov/learners
  44. http://www.mtu.edu/