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 23
    [2]The featured image shows the Sun in X-ray light as shown by NASA's
   NuSTAR satellite -- superimposed on an image in ultraviolet light taken
     by NASA's Solar Dynamic Observatory. Please see the explanation for
                         more detailed information.

                        The Sun in X-rays from NuSTAR
                  Image Credit: [3]NASA, [4]NuSTAR, [5]SDO

   Explanation: Why are the regions above sunspots so hot? [6]Sunspots
   themselves are a bit cooler than the surrounding solar surface because
   the magnetic fields that create them reduce [7]convective heating. It
   is therefore unusual that regions overhead -- even much higher up in
   the [8]Sun's corona -- can be hundreds of times hotter. To help find
   the cause, [9]NASA directed the Earth-orbiting [10]Nuclear
   Spectroscopic Telescope Array (NuSTAR) satellite to point its very
   sensitive X-ray telescope at the Sun. [11]Featured here is the Sun in
   [12]ultraviolet light, [13]shown in a red hue as taken by the orbiting
   [14]Solar Dynamics Observatory (SDO). Superimposed in false-colored
   green and blue is emission above [15]sunspots detected by [16]NuSTAR in
   different bands of high-energy [17]X-rays, highlighting regions of
   extremely [18]high temperature. Clues about the Sun's atmospheric
   [19]heating mechanisms come from NuSTAR images like this and shed light
   on solar [20]nanoflares and [21]microflares as brief [22]bursts of
   energy that may drive the unusual heating.

                     Tomorrow's picture: stellar sisters
     __________________________________________________________________

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    Authors & editors: [34]Robert Nemiroff ([35]MTU) & [36]Jerry Bonnell
                                 ([37]UMCP)
          NASA Official: Phillip Newman [38]Specific rights apply.
              [39]NASA Web Privacy Policy and Important Notices
                A service of: [40]ASD at [41]NASA / [42]GSFC
                           & [43]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2111/ActiveSun_NuSTAR_1600.jpg
   3. https://www.nasa.gov/
   4. https://www.nasa.gov/mission_pages/nustar/main/index.html
   5. https://sdo.gsfc.nasa.gov/
   6. https://en.wikipedia.org/wiki/Sunspot
   7. https://www.youtube.com/watch?v=VxGIiOTuAIs
   8. https://apod.nasa.gov/apod/ap190701.html
   9. https://twitter.com/nasa
  10. https://www.nustar.caltech.edu/news/nustar141222
  11. https://www.nustar.caltech.edu/news/nustar141222
  12. https://science.nasa.gov/ems/10_ultravioletwaves
  13. https://www.jpl.nasa.gov/images/sun-shines-in-high-energy-x-rays
  14. https://sdo.gsfc.nasa.gov/mission/
  15. https://spaceplace.nasa.gov/solar-activity/en/
  16. https://en.wikipedia.org/wiki/NuSTAR
  17. https://science.nasa.gov/ems/11_xrays
  18. https://www.youtube.com/watch?v=4fuHzC9aTik
  19. https://apod.nasa.gov/apod/ap050814.html
  20. https://en.wikipedia.org/wiki/Nanoflares
  21. https://ui.adsabs.harvard.edu/abs/2021MNRAS.507.3936C/abstract
  22. https://images.fineartamerica.com/images-medium-large-5/jumping-kitten-akimasa-harada.jpg
  23. https://apod.nasa.gov/apod/ap211122.html
  24. https://apod.nasa.gov/apod/archivepix.html
  25. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  26. https://apod.nasa.gov/apod/lib/aptree.html
  27. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  28. https://apod.nasa.gov/apod/calendar/allyears.html
  29. https://apod.nasa.gov/apod.rss
  30. https://apod.nasa.gov/apod/lib/edlinks.html
  31. https://apod.nasa.gov/apod/lib/about_apod.html
  32. http://asterisk.apod.com/discuss_apod.php?date=211123
  33. https://apod.nasa.gov/apod/ap211124.html
  34. http://www.phy.mtu.edu/faculty/Nemiroff.html
  35. http://www.phy.mtu.edu/
  36. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  37. http://www.astro.umd.edu/
  38. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  39. https://www.nasa.gov/about/highlights/HP_Privacy.html
  40. https://astrophysics.gsfc.nasa.gov/
  41. https://www.nasa.gov/
  42. https://www.nasa.gov/centers/goddard/
  43. http://www.mtu.edu/