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.

                               2019 October 6
    [2]See Explanation. Clicking on the picture will download the highest
                        resolution version available.

                            The Horsehead Nebula
             Image Credit & Copyright: [3]José Jiménez Priego

   Explanation: The [4]Horsehead Nebula is one of the most famous nebulae
   on the sky. It is visible as the dark indentation to the red
   [5]emission nebula in the center of the above photograph. The
   [6]horse-head feature is dark because it is really an opaque [7]dust
   cloud that lies in front of the bright red [8]emission nebula. Like
   clouds in [9]Earth's atmosphere, this cosmic cloud has assumed a
   [10]recognizable shape by chance. After many thousands of years, the
   internal motions of the cloud will surely alter its appearance. The
   emission [11]nebula's red color is caused by [12]electrons recombining
   with [13]protons to form [14]hydrogen atoms. On the image left is the
   [15]Flame Nebula, an orange-tinged nebula that also contains filaments
   of dark dust. Just to the lower left of the Horsehead nebula
   [16]featured picture is a blueish [17]reflection nebulae that
   preferentially [18]reflects the blue light from [19]nearby stars.

                     Tomorrow's picture: jupiter spotted
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    Authors & editors: [31]Robert Nemiroff ([32]MTU) & [33]Jerry Bonnell
                                 ([34]UMCP)
          NASA Official: Phillip Newman [35]Specific rights apply.
              [36]NASA Web Privacy Policy and Important Notices
                A service of: [37]ASD at [38]NASA / [39]GSFC
                           & [40]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/1910/HorseFlame_Priego_3252.jpg
   3. https://www.facebook.com/jose.jimenezjj
   4. https://en.wikipedia.org/wiki/Horsehead_nebula
   5. https://apod.nasa.gov/apod/emission_nebulae.html
   6. https://apod.nasa.gov/apod/ap140728.html
   7. https://apod.nasa.gov/apod/ap030706.html
   8. https://en.wikipedia.org/wiki/Emission_nebula
   9. http://www.nasa.gov/mission_pages/sunearth/science/atmosphere-layers2.html
  10. http://www.brucevanpatter.com/cloudshapes.html
  11. https://apod.nasa.gov/apod/ap061015.html
  12. http://www.pbs.org/transistor/science/events/electron.html
  13. http://hyperphysics.phy-astr.gsu.edu/hbase/particles/proton.html
  14. http://periodic.lanl.gov/1.shtml
  15. https://apod.nasa.gov/apod/ap141209.html
  16. https://www.flickr.com/photos/astromet/21844852965/in/album-72157634385115181/
  17. https://apod.nasa.gov/apod/reflection_nebulae.html
  18. https://spaceplace.nasa.gov/blue-sky/en/
  19. https://apod.nasa.gov/apod/ap010318.html
  20. https://apod.nasa.gov/apod/ap191005.html
  21. https://apod.nasa.gov/apod/archivepix.html
  22. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  23. https://apod.nasa.gov/apod/lib/aptree.html
  24. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  25. https://apod.nasa.gov/apod/calendar/allyears.html
  26. https://apod.nasa.gov/apod.rss
  27. https://apod.nasa.gov/apod/lib/edlinks.html
  28. https://apod.nasa.gov/apod/lib/about_apod.html
  29. http://asterisk.apod.com/discuss_apod.php?date=191006
  30. https://apod.nasa.gov/apod/ap191007.html
  31. http://www.phy.mtu.edu/faculty/Nemiroff.html
  32. http://www.phy.mtu.edu/
  33. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  34. http://www.astro.umd.edu/
  35. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  36. https://www.nasa.gov/about/highlights/HP_Privacy.html
  37. https://astrophysics.gsfc.nasa.gov/
  38. https://www.nasa.gov/
  39. https://www.nasa.gov/centers/goddard/
  40. http://www.mtu.edu/