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! __________________________________________________________________ [27]< | [28]Archive | [29]Submissions | [30]Index | [31]Search | [32]Calendar | [33]RSS | [34]Education | [35]About APOD | [36]Discuss | [37]> __________________________________________________________________ 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/