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.

                                2026 March 18
     [2]Clouds of gas glow red in the night sky above a dark tree on the
    horizon that stands in a meadow. Please see the explanation for more
                            detailed information.

                        Cygnus and the Solitary Tree
       Image Credit & Copyright: 2025 Horacio Lander / [3]AstroHoracio
   Text: [4]Keighley Rockcliffe ([5]NASA [6]GSFC, [7]UMBC CSST, [8]CRESST
                                     II)

   Explanation: A lone tree stands in a quiet meadow in [9]Guadalajara,
   Spain, silhouetted against [10]the Cygnus region rising above like
   flames in the night sky. This deep night skyscape is a composite of
   exposures that reveals a range of brightness and color human eyes can't
   quite see on their own. Spanning over a thousand times the [11]angular
   size of the full moon, [12]Cygnus sets the sky afire with [13]active
   star formation where clouds of gas and dust collapse under gravity
   until [14]nuclear fusion ignites and new stars are born. These stars
   [15]ionize the surrounding hydrogen gas, causing it to [16]glow
   crimson, while tendrils of [17]interstellar dust absorb some of that
   light and cast dark shadows across the sky. Cygnus is a trove of
   celestial treasures, notably the [18]Veil, [19]Crescent, and
   [20]Pelican nebulae, as well as [21]Cygnus X-1, the first confirmed
   [22]black hole. Cygnus continues to yield fresh science, including
   [23]a new three-dimensional model of the [24]Cygnus Loop made possible
   by [25]the Chandra X-ray Observatory.

                Almost Hyperspace: [26]Random APOD Generator
                      Tomorrow's picture: A Jellyfish!
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    Authors & editors: [38]Robert Nemiroff ([39]MTU) & [40]Jerry Bonnell
                                 ([41]UMCP)
          NASA Official: Amber Straughn [42]Specific rights apply.
            [43]NASA Web Privacy, [44]Accessibility, [45]Notices;
                A service of: [46]ASD at [47]NASA / [48]GSFC,
                         [49]NASA Science Activation
                           & [50]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2603/cygnus_tree_crop.jpg
   3. http://astrohoracio.com/
   4. https://kerockcliffe.com/
   5. https://science.gsfc.nasa.gov/sci/bio/keighley.e.rockcliffe
   6. https://www.nasa.gov/goddard/
   7. https://csst.umbc.edu/directory/
   8. https://cresst2.umd.edu/
   9. https://www.guadalajara.es/en/tourism/discover-guadalajara/
  10. https://apod.nasa.gov/apod/ap210211.html
  11. https://earthsky.org/astronomy-essentials/sky-measurements-degrees-arc-minutes-arc-seconds/
  12. https://noirlab.edu/public/education/constellations/cygnus/
  13. https://courses.lumenlearning.com/towson-astronomy/chapter/star-formation/
  14. https://courses.ems.psu.edu/astro801/content/l5_p4.html
  15. https://energyeducation.ca/encyclopedia/Ionization
  16. https://science.nasa.gov/mission/webb/science-overview/science-explainers/spectroscopy-101-how-absorption-and-emission-spectra-work/
  17. https://apod.nasa.gov/apod/ap251119.html
  18. https://apod.nasa.gov/apod/ap250602.html
  19. https://apod.nasa.gov/apod/ap251128.html
  20. https://apod.nasa.gov/apod/ap210301.html
  21. https://apod.nasa.gov/apod/ap240828.html
  22. https://science.nasa.gov/universe/black-holes/
  23. https://chandra.harvard.edu/deadstar/cygnus.html
  24. https://apod.nasa.gov/apod/ap200928.html
  25. https://www.nasa.gov/mission/chandra-x-ray-observatory/
  26. https://apod.nasa.gov/apod/random_apod.html
  27. https://apod.nasa.gov/apod/ap260317.html
  28. https://apod.nasa.gov/apod/archivepix.html
  29. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  30. https://apod.nasa.gov/apod/lib/aptree.html
  31. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  32. https://apod.nasa.gov/apod/calendar/allyears.html
  33. https://apod.com/feed.rss
  34. https://apod.nasa.gov/apod/lib/edlinks.html
  35. https://apod.nasa.gov/apod/lib/about_apod.html
  36. https://asterisk.apod.com/discuss_apod.php?date=260318
  37. https://apod.nasa.gov/apod/ap260319.html
  38. http://www.phy.mtu.edu/faculty/Nemiroff.html
  39. http://www.phy.mtu.edu/
  40. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  41. http://www.astro.umd.edu/
  42. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  43. https://www.nasa.gov/about/highlights/HP_Privacy.html
  44. https://www.nasa.gov/general/accessibility/
  45. https://www.nasa.gov/privacy/
  46. https://astrophysics.gsfc.nasa.gov/
  47. https://www.nasa.gov/
  48. https://www.nasa.gov/centers/goddard/
  49. https://science.nasa.gov/learners
  50. http://www.mtu.edu/