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 __________________________________________________________________ [19]< | [20]Archive | [21]Submissions | [22]Index | [23]Search | [24]Calendar | [25]RSS | [26]Education | [27]About APOD | [28]Discuss | [29]> __________________________________________________________________ Authors & editors: [30]Robert Nemiroff ([31]MTU) & [32]Jerry Bonnell ([33]UMCP) NASA Official: Phillip Newman [34]Specific rights apply. [35]NASA Web Privacy Policy and Important Notices 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/