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.

                                2021 July 21
   [2]The picture shows the several images of the Ring Nebula separated by
   their colors. Please see the explanation for more detailed information.

                      Colors: Ring Nebula versus Stars
             Image Credit: [3]Robert Vanderbei ([4]Princeton U.)

   Explanation: What if you could see, separately, all the [5]colors of
   the Ring? And of the surrounding stars? There's technology for that.
   The [6]featured image shows the [7]Ring Nebula (M57) and nearby stars
   through such technology: in this case, a [8]prism-like [9]diffraction
   grating. The [10]Ring Nebula is seen only a few times because it emits
   light, primarily, in only a few colors. The two brightest emitted
   colors are [11]hydrogen ([12]red) and [13]oxygen (blue), appearing as
   nearly overlapping images to the left of the image center. The image
   just to the right of center is the [14]color-combined icon normally
   seen. Stars, on the other hand, emit most of their light in colors all
   across the [15]visible spectrum. These colors, [16]combined, make a
   nearly continuous streak -- which is why stars appear accompanied by
   multicolored bars. Breaking object light up into colors is
   [17]scientifically useful because it can reveal the [18]elements that
   compose that object, [19]how fast that object is moving, and [20]how
   distant that object is.

                       Tomorrow's picture: open space
     __________________________________________________________________

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    Authors & editors: [32]Robert Nemiroff ([33]MTU) & [34]Jerry Bonnell
                                 ([35]UMCP)
          NASA Official: Phillip Newman [36]Specific rights apply.
              [37]NASA Web Privacy Policy and Important Notices
                A service of: [38]ASD at [39]NASA / [40]GSFC
                           & [41]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2107/RingColorsOH_Vanderbei_1400.jpg
   3. https://vanderbei.princeton.edu/
   4. https://orfe.princeton.edu/
   5. https://youtu.be/O9MvdMqKvpU?t=87
   6. https://vanderbei.princeton.edu/images/NJP/m57.html
   7. https://www.nasa.gov/feature/goddard/2017/messier-57-the-ring-nebula
   8. https://en.wikipedia.org/wiki/Prism#/media/File:Light_dispersion_conceptual_waves.gif
   9. https://en.wikipedia.org/wiki/Diffraction_grating
  10. https://apod.nasa.gov/apod/ap180417.html
  11. https://periodic.lanl.gov/1.shtml
  12. https://en.wikipedia.org/wiki/H-alpha
  13. https://www.nasa.gov/press-release/nasa-s-perseverance-mars-rover-extracts-first-oxygen-from-red-planet
  14. https://apod.nasa.gov/apod/ap060511.html
  15. https://science.nasa.gov/ems/09_visiblelight
  16. https://s36537.pcdn.co/wp-content/uploads/2015/06/snuggle_01.jpg.optimal.jpg
  17. https://imagine.gsfc.nasa.gov/science/toolbox/spectra1.html
  18. https://apod.nasa.gov/apod/ap200809.html
  19. https://en.wikipedia.org/wiki/Doppler_spectroscopy
  20. https://apod.nasa.gov/apod/ap200920.html
  21. https://apod.nasa.gov/apod/ap210720.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.nasa.gov/apod.rss
  28. https://apod.nasa.gov/apod/lib/edlinks.html
  29. https://apod.nasa.gov/apod/lib/about_apod.html
  30. http://asterisk.apod.com/discuss_apod.php?date=210721
  31. https://apod.nasa.gov/apod/ap210722.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://astrophysics.gsfc.nasa.gov/
  39. https://www.nasa.gov/
  40. https://www.nasa.gov/centers/goddard/
  41. http://www.mtu.edu/