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 September 17
   [2]A starfield surrounds a several large nebulas that appear mostly red
   but also white and blue. Dark dust and blue filaments also populate the
      frame. Please see the explanation for more detailed information.

                     Nebulas and Clusters in Sagittarius
   Image Credit & Copyright: [3]J. De Winter, [4]C. Humbert, [5]C. Robert
               & [6]V. Sabet; Text: [7]Ogetay Kayali ([8]MTU)

   Explanation: Can you spot famous celestial objects in this image?
   18th-century astronomer [9]Charles Messier cataloged only two of them:
   the bright [10]Lagoon Nebula (M8) at the bottom, and the colorful
   [11]Trifid Nebula (M20) at the upper right. The one on the left that
   resembles a [12]cat's paw is [13]NGC 6559, and it is much fainter than
   the other two. Even harder to spot are the thin blue filaments on the
   left, from [14]supernova remnant (SNR G007.5-01.7). Their glow comes
   from small amounts of [15]glowing oxygen atoms that are so faint that
   it took over [16]17 hours of exposure with just one blue color to bring
   up. Framing this scene of stellar birth and death are two star
   clusters: the [17]open cluster [18]M21 just above Trifid, and the
   [19]globular cluster [20]NGC 6544 at lower left.

                        Tomorrow's picture: NGC 6914
     __________________________________________________________________

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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/2509/SagNebs_DeWinter_4550.jpg
   3. https://www.instagram.com/dwj85
   4. https://www.instagram.com/astro.berto54
   5. https://www.instagram.com/charlesrbert
   6. https://app.astrobin.com/u/victorf#gallery
   7. https://www.ogetay.com/
   8. https://www.mtu.edu/physics/
   9. https://science.nasa.gov/people/explore-the-night-sky-hubbleatms-messier-catalog-bio/
  10. https://apod.nasa.gov/apod/ap250625.html
  11. https://apod.nasa.gov/apod/ap240704.html
  12. https://people.com/thmb/-ZwPce1JwYWjaTIEYYXePkDAFWo=/4000x0/filters:no_upscale():max_bytes(150000):strip_icc():focal(144x0:146x2)/000829300-1-166c18e3f54846d287baa774ae29b18e.jpg
  13. https://apod.nasa.gov/apod/ap230710.html
  14. https://science.gsfc.nasa.gov/662/research/snrs.html
  15. https://en.wikipedia.org/wiki/Doubly_ionized_oxygen
  16. https://app.astrobin.com/i/jliezm
  17. https://en.wikipedia.org/wiki/Open_cluster
  18. https://en.wikipedia.org/wiki/Messier_21
  19. https://en.wikipedia.org/wiki/Globular_cluster
  20. https://esahubble.org/images/potw2325a/
  21. https://apod.nasa.gov/apod/ap250916.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=250917
  31. https://apod.nasa.gov/apod/ap250918.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/