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 November 29
    [2]The featured image shows an unusual spiral structure in the binary
   star system LL Pegasi as captured by the Hubble Space Telescope. Please
             see the explanation for more detailed information.

                    The Extraordinary Spiral in LL Pegasi
       Image Credit: [3]NASA, [4]ESA, [5]Hubble, [6]HLA; Processing &
                        Copyright: [7]Jonathan Lodge

   Explanation: What created the strange spiral structure on the upper
   left? No one is sure, although it is likely related to a star in a
   [8]binary star system entering the [9]planetary nebula phase, when its
   outer atmosphere is ejected. The [10]huge spiral spans about a third of
   a [11]light year across and, winding four or five [12]complete turns,
   has a regularity that is without precedent. Given the expansion rate of
   the [13]spiral gas, a new layer must appear about every 800 years, a
   close match to the time it takes for the two stars to orbit each other.
   The [14]star system that created it is most commonly known as [15]LL
   Pegasi, but also AFGL 3068 and IRAS 23166+1655. The featured image was
   taken in near-[16]infrared light by the [17]Hubble Space Telescope. Why
   the [18]spiral glows is [19]itself a mystery, with a leading hypothesis
   being illumination by light reflected from nearby stars.

                    Tomorrow's picture: planet with moons
     __________________________________________________________________

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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/2111/LLPegasi_HubbleLodge_1926.jpg
   3. https://www.nasa.gov/
   4. https://www.esa.int/
   5. https://www.nasa.gov/mission_pages/hubble/story/index.html
   6. https://hla.stsci.edu/
   7. https://www.instagram.com/jjlodge/
   8. https://apod.nasa.gov/apod/ap970219.html
   9. https://en.wikipedia.org/wiki/Planetary_nebula
  10. https://apod.nasa.gov/apod/ap210124.html
  11. https://chandra.harvard.edu/photo/cosmic_distance.html
  12. https://www.eso.org/public/images/potw1710a/
  13. https://en.wikipedia.org/wiki/Spiral
  14. https://www.eso.org/public/videos/potw1710a/
  15. https://en.wikipedia.org/wiki/LL_Pegasi
  16. https://science.nasa.gov/ems/07_infraredwaves
  17. https://hubblesite.org/mission-and-telescope
  18. http://flyingpudding.com/projects/florets/applet/
  19. https://www.intermountainpet.com/hs-fs/hubfs/Blog_Images/Dogs-tilting-their-heads.jpg?width=900&name=Dogs-tilting-their-heads.jpg
  20. https://apod.nasa.gov/apod/ap211128.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=211129
  30. https://apod.nasa.gov/apod/ap211130.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/