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.

                               2022 November 9
     [2]The featured image shows a complex nebula that is more dense and
    more blue on one side than the other. Please see the explanation for
                         more detailed information.

            The Asymmetric Nebula Surrounding Wolf-Rayet Star 18
                  Image Credit & Copyright: [3]Alex Woronow

   Explanation: Why does the nebula around the star WR-18 shine brighter
   on one side? Also known as [4]NGC 3199, this active star and its
   surrounding nebula lie about 12,000 [5]light-years away toward the
   nautical southern constellation [6]of Carina. The [7]featured deep
   image has been highly processed to bring out filamentary details of the
   glowing gas in the bubble-shaped nebula. The nebula is about 75
   light-years across. Near the nebula's center is a [8]Wolf-Rayet star,
   WR-18, which is a massive, hot, short-lived star that generates an
   intense and complex stellar wind. In fact, [9]Wolf-Rayet stars are
   known to create nebulas with [10]interesting shapes as their powerful
   winds sweep up surrounding [11]interstellar material. In this case, the
   bright right edge was initially thought to indicate that a [12]bow
   shock was being produced as the star plowed through a uniform medium,
   like a [13]boat through water. [14]Recent measurements and
   analys[15]e[16]s, however, have shown the star is [17]not moving
   quickly toward the bright edge. A more likely explanation has
   [18]emerged that the material surrounding the star is not uniform, but
   clumped and denser near the bright edge.

                       Tomorrow's picture: open space
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    Authors & editors: [30]Robert Nemiroff ([31]MTU) & [32]Jerry Bonnell
                                 ([33]UMCP)
          NASA Official: Phillip Newman [34]Specific rights apply.
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                A service of: [36]ASD at [37]NASA / [38]GSFC,
                         [39]NASA Science Activation
                           & [40]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2211/wr18_woronow_2048.jpg
   3. https://www.astrobin.com/users/Alex_Woronow/
   4. https://en.wikipedia.org/wiki/NGC_3199
   5. https://spaceplace.nasa.gov/light-year/en/
   6. http://www.hawastsoc.org/deepsky/car/index.html
   7. https://www.astrobin.com/x0kpsk/
   8. https://astrobiology.nasa.gov/news/a-wolf-rayet-bubble-and-the-early-solar-system/
   9. https://apod.nasa.gov/apod/ap200308.html
  10. https://apod.nasa.gov/apod/ap200612.html
  11. http://www-ssg.sr.unh.edu/ism/what1.html
  12. https://apod.nasa.gov/apod/ap200202.html
  13. https://en.wikipedia.org/wiki/Bow_wave
  14. https://ui.adsabs.harvard.edu/abs/2017ApJ...846...76T/abstract
  15. https://ui.adsabs.harvard.edu/abs/2001ApJ...563..875M/abstract
  16. https://ui.adsabs.harvard.edu/abs/2017ApJ...846...76T/abstract
  17. https://image.shutterstock.com/image-photo/funny-british-kitten-looks-surprise-260nw-1221814405.jpg
  18. https://ui.adsabs.harvard.edu/abs/2001ApJ...563..875M/abstract
  19. https://apod.nasa.gov/apod/ap221108.html
  20. https://apod.nasa.gov/apod/archivepix.html
  21. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  22. https://apod.nasa.gov/apod/lib/aptree.html
  23. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  24. https://apod.nasa.gov/apod/calendar/allyears.html
  25. https://apod.nasa.gov/apod.rss
  26. https://apod.nasa.gov/apod/lib/edlinks.html
  27. https://apod.nasa.gov/apod/lib/about_apod.html
  28. http://asterisk.apod.com/discuss_apod.php?date=221109
  29. https://apod.nasa.gov/apod/ap221110.html
  30. http://www.phy.mtu.edu/faculty/Nemiroff.html
  31. http://www.phy.mtu.edu/
  32. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  33. http://www.astro.umd.edu/
  34. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  35. https://www.nasa.gov/about/highlights/HP_Privacy.html
  36. https://astrophysics.gsfc.nasa.gov/
  37. https://www.nasa.gov/
  38. https://www.nasa.gov/centers/goddard/
  39. https://science.nasa.gov/learners
  40. http://www.mtu.edu/