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 July 29
   [2]A nearly circular nebula with a blue core surrounded by small white
      knots, an orange ring and expansive red strucures. Please see the
                 explanation for more detailed information.

                          A Helix Nebula Deep Field
             Image Credit & Copyright: [3]George Chatzifrantzis

   Explanation: Is the Helix Nebula looking at you? No, not in any
   biological sense, but it does look quite like an eye. The [4]Helix
   Nebula is so named because it also appears that you are looking down
   the axis of a [5]helix. In actuality, it is now understood to have a
   surprisingly [6]complex geometry, including radial filaments and
   extended [7]outer loops. The Helix Nebula ([8]aka NGC 7293) is one of
   brightest and closest examples of a [9]planetary nebula, a gas
   [10]cloud created at the end of the life of a Sun-like star. The
   remnant central stellar core, destined to become a [11]white dwarf
   star, glows in light so [12]energetic it causes the previously expelled
   gas to [13]fluoresce. The [14]featured picture, taken in red, green,
   and blue but highlighted by light emitted primarily by [15]hydrogen was
   created from 12 hours of exposure through a personal telescope located
   in [16]Greece. A [17]close-up of the [18]inner edge of the Helix Nebula
   shows complex gas knots the origin of which are [19]still being
   researched.

                 Portal Universe: [20]Random APOD Generator
                        Tomorrow's picture: loopy Sun
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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/2507/Helix_GC_2332.jpg
   3. https://www.facebook.com/GeorgeChatzifrantzis
   4. https://en.wikipedia.org/wiki/Helix_Nebula
   5. http://mathworld.wolfram.com/Helix.html
   6. https://chandra.harvard.edu/deadstar/helix.html
   7. https://apod.nasa.gov/apod/ap230507.html
   8. https://grammarist.com/acronym/a-k-a-or-aka/
   9. https://en.wikipedia.org/wiki/Planetary_nebula
  10. http://www.youtube.com/watch?v=KXNSYo8ZdoU
  11. https://apod.nasa.gov/apod/ap231224.html
  12. https://science.nasa.gov/ems/10_ultravioletwaves
  13. https://youtu.be/WnWIt0iz00A
  14. https://www.facebook.com/photo/?fbid=729866973075216&set=a.149603584434894
  15. http://www.astronomyknowhow.com/hydrogen-alpha.htm
  16. https://en.wikipedia.org/wiki/Greece
  17. http://www.youtube.com/watch?v=UwAKNMC2PeM
  18. https://apod.nasa.gov/apod/ap080413.html
  19. https://ui.adsabs.harvard.edu/abs/2020MNRAS.491..758A/abstract
  20. https://apod.nasa.gov/apod/random_apod.html
  21. https://apod.nasa.gov/apod/ap250728.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=250729
  31. https://apod.nasa.gov/apod/ap250730.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/