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.

                               2023 October 4
    [2]A colorful star field surrounds a big blue reflection nebula. The
   nebula is elongated across the wide frame and said to resemble the head
    of folklore-based witch. Please see the explanation for more detailed
                                information.

                       IC 2118: The Witch Head Nebula
                Image Credit & Copyright: [3]Abdullah Alharbi

   Explanation: Does this nebula look like the head of a witch? The nebula
   is [4]known popularly as the Witch Head Nebula because, it is said, the
   nebula's shape resembles a [5]Halloween-style caricature of a witch's
   head. Exactly how, though, can be a topic of imaginative speculation.
   What is clear is that [6]IC 2118 is about 50 [7]light-years across and
   made of gas and dust that points to -- because it has been partly
   eroded by -- the nearby star [8]Rigel. One of the brighter stars in the
   constellation Orion, [9]Rigel lies below the bottom of the [10]featured
   image. The blue color of the Witch Head Nebula and is caused not only
   by [11]Rigel's intense blue starlight but because the [12]dust grains
   scatter blue light more efficiently than red. The same [13]physical
   process causes Earth's daytime [14]sky to appear blue, although the
   scatterers in planet [15]Earth's atmosphere are molecules of
   [16]nitrogen and [17]oxygen.

                       Tomorrow's picture: open space
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    Authors & editors: [29]Robert Nemiroff ([30]MTU) & [31]Jerry Bonnell
                                 ([32]UMCP)
          NASA Official: Phillip Newman [33]Specific rights apply.
              [34]NASA Web Privacy Policy and Important Notices
                A service of: [35]ASD at [36]NASA / [37]GSFC,
                         [38]NASA Science Activation
                           & [39]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2310/WitchHead_Alharbi_3051.jpg
   3. https://www.instagram.com/a_alharbi97/
   4. https://earthsky.org/todays-image/witch-head-nebula-orion/
   5. https://en.wikipedia.org/wiki/Halloween#/media/File:Halloween_Witch_2011.JPG
   6. https://en.wikipedia.org/wiki/IC_2118
   7. https://spaceplace.nasa.gov/light-year/
   8. https://en.wikipedia.org/wiki/Rigel
   9. https://apod.nasa.gov/apod/ap230407.html
  10. https://www.instagram.com/p/CqdsZ47M7xc/
  11. https://apod.nasa.gov/apod/ap220124.html
  12. https://curator.jsc.nasa.gov/dust/
  13. http://hyperphysics.phy-astr.gsu.edu/hbase/atmos/blusky.html
  14. https://spaceplace.nasa.gov/blue-sky/en/
  15. https://www.nasa.gov/image-article/earths-atmospheric-layers-3/
  16. https://www.nasa.gov/solar-system/nasas-curiosity-rover-finds-biologically-useful-nitrogen-on-mars/
  17. https://astrobiology.nasa.gov/news/lightning-oxygen-and-life-detection/
  18. https://apod.nasa.gov/apod/ap231003.html
  19. https://apod.nasa.gov/apod/archivepix.html
  20. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  21. https://apod.nasa.gov/apod/lib/aptree.html
  22. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  23. https://apod.nasa.gov/apod/calendar/allyears.html
  24. https://apod.nasa.gov/apod.rss
  25. https://apod.nasa.gov/apod/lib/edlinks.html
  26. https://apod.nasa.gov/apod/lib/about_apod.html
  27. https://asterisk.apod.com/discuss_apod.php?date=231004
  28. https://apod.nasa.gov/apod/ap231005.html
  29. http://www.phy.mtu.edu/faculty/Nemiroff.html
  30. http://www.phy.mtu.edu/
  31. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  32. http://www.astro.umd.edu/
  33. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  34. https://www.nasa.gov/about/highlights/HP_Privacy.html
  35. https://astrophysics.gsfc.nasa.gov/
  36. https://www.nasa.gov/
  37. https://www.nasa.gov/centers/goddard/
  38. https://science.nasa.gov/learners
  39. http://www.mtu.edu/