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                        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 February 10
    [2]See Explanation. Clicking on the picture will download the highest
                        resolution version available.

                        Firing Lasers to Tame the Sky
   Image Credit & Copyright: [3]Juan Carlos Muñoz / [4]ESO; Text: [5]Juan
                                Carlos Muñoz

   Explanation: Why do stars twinkle? [6]Our atmosphere is to blame as
   pockets of slightly off-temperature air, in constant motion, distort
   the light paths from distant astronomical objects. Atmospheric
   turbulence is a problem for astronomers because it [7]blurs the images
   of the sources they want to study. The telescope featured in this
   image, located at [8]ESO's [9]Paranal Observatory, is equipped with
   [10]four lasers to combat [11]this turbulence. The lasers are tuned to
   a color that excites atoms floating high in [12]Earth's atmosphere --
   [13]sodium left by passing meteors. These [14]glowing sodium spots act
   as artificial stars whose twinkling is immediately recorded and passed
   to a [15]flexible mirror that deforms hundreds of times per second,
   counteracting atmospheric turbulence and resulting in [16]crisper
   images. The [17]de-twinkling of stars is a developing field of
   technology and allows, in some cases, [18]Hubble-[19]class [20]images
   to be taken from the ground. This technique has also led to spin-off
   applications in [21]human vision science, where it is used to obtain
   very sharp images of the retina.

                       Tomorrow's picture: open space
     __________________________________________________________________

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    Authors & editors: [33]Robert Nemiroff ([34]MTU) & [35]Jerry Bonnell
                                 ([36]UMCP)
          NASA Official: Phillip Newman [37]Specific rights apply.
              [38]NASA Web Privacy Policy and Important Notices
                A service of: [39]ASD at [40]NASA / [41]GSFC
                           & [42]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2102/AoLasers_Munoz_3648.jpg
   3. https://twitter.com/astro_jcm
   4. https://www.eso.org/public/
   5. https://twitter.com/astro_jcm
   6. https://en.wikipedia.org/wiki/Astronomical_seeing
   7. https://www.youtube.com/watch?v=or1A4g14_jM
   8. https://www.eso.org/
   9. https://www.eso.org/public/teles-instr/paranal-observatory/
  10. https://www.eso.org/public/teles-instr/paranal-observatory/vlt/vlt-instr/4lgsf/
  11. https://apod.nasa.gov/apod/ap000725.html
  12. https://www.nasa.gov/sites/default/files/images/463940main_atmosphere-layers2_full.jpg
  13. https://en.wikipedia.org/wiki/Sodium_layer
  14. http://sguisard.astrosurf.com/Pagim/M42-4LGS.html
  15. https://www.youtube.com/watch?v=gDGvNyVApgg
  16. https://www.eso.org/public/images/eso1824b/
  17. https://en.wikipedia.org/wiki/Adaptive_optics
  18. https://www.nasa.gov/audience/forstudents/5-8/features/nasa-knows/what-is-the-hubble-space-telecope-58.html
  19. https://apod.nasa.gov/apod/ap201206.html
  20. https://apod.nasa.gov/apod/ap181009.html
  21. https://www.alpao.com/adaptive-optics/ophtalmology.html
  22. https://apod.nasa.gov/apod/ap210209.html
  23. https://apod.nasa.gov/apod/archivepix.html
  24. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  25. https://apod.nasa.gov/apod/lib/aptree.html
  26. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  27. https://apod.nasa.gov/apod/calendar/allyears.html
  28. https://apod.nasa.gov/apod.rss
  29. https://apod.nasa.gov/apod/lib/edlinks.html
  30. https://apod.nasa.gov/apod/lib/about_apod.html
  31. http://asterisk.apod.com/discuss_apod.php?date=210210
  32. https://apod.nasa.gov/apod/ap210211.html
  33. http://www.phy.mtu.edu/faculty/Nemiroff.html
  34. http://www.phy.mtu.edu/
  35. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  36. http://www.astro.umd.edu/
  37. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  38. https://www.nasa.gov/about/highlights/HP_Privacy.html
  39. https://astrophysics.gsfc.nasa.gov/
  40. https://www.nasa.gov/
  41. https://www.nasa.gov/centers/goddard/
  42. http://www.mtu.edu/