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 October 21 [2]See Explanation. Clicking on the picture will download the highest resolution version available. SH2-308: The Dolphin-Head Nebula Image Credit & [3]Copyright: [4]Nik Szymanek Explanation: Blown by fast winds from a hot, massive star, this cosmic bubble is huge. Cataloged as [5]Sharpless 2-308 it lies some 5,000 light-years away toward the constellation of the Big Dog ([6]Canis Major) and covers slightly more of the sky than a Full Moon. That [7]corresponds to a diameter of 60 light-years at its estimated distance. The massive star that created the bubble, a [8]Wolf-Rayet star, is the bright one [9]near the center of the nebula. [10]Wolf-Rayet stars have over 20 times the mass of the Sun and are thought to be in a brief, [11]pre-supernova phase of massive star evolution. Fast winds from this [12]Wolf-Rayet star create the bubble-shaped nebula as they sweep up slower moving material from an earlier phase of evolution. The [13]windblown nebula has an age of about [14]70,000 years. Relatively faint emission captured by narrowband filters in the deep image is dominated by the glow of ionized oxygen atoms [15]mapped to a blue hue. Presenting a [16]mostly harmless outline, SH2-308 is also known as The Dolphin-head Nebula. Tomorrow's picture: it's a comet __________________________________________________________________ [17]< | [18]Archive | [19]Submissions | [20]Index | [21]Search | [22]Calendar | [23]RSS | [24]Education | [25]About APOD | [26]Discuss | [27]> __________________________________________________________________ Authors & editors: [28]Robert Nemiroff ([29]MTU) & [30]Jerry Bonnell ([31]UMCP) NASA Official: Phillip Newman [32]Specific rights apply. [33]NASA Web Privacy Policy and Important Notices A service of: [34]ASD at [35]NASA / [36]GSFC & [37]Michigan Tech. U. References 1. https://apod.nasa.gov/apod/archivepix.html 2. https://apod.nasa.gov/apod/image/2110/SH2-308NS.jpg 3. https://apod.nasa.gov/apod/lib/about_apod.html#srapply 4. http://www.ccdland.net/ 5. http://galaxymap.org/cat/list/sharpless/301 6. https://en.wikipedia.org/wiki/Canis_Major 7. http://chandra.harvard.edu/photo/scale_distance.html 8. http://en.wikipedia.org/wiki/Wolf-Rayet_star 9. https://en.wikipedia.org/wiki/EZ_Canis_Majoris 10. http://earthsky.org/space/wolf-rayets-are-the-most-massive-and-brightest-stars-known 11. https://apod.nasa.gov/apod/ap030325.html 12. https://www.nasa.gov/image-feature/goddard/hubble-view-wolf-rayet-stars-intense-and-short-lived 13. https://apod.nasa.gov/apod/ap080522.html 14. http://en.wikipedia.org/wiki/Middle_Paleolithic 15. https://hubblesite.org/contents/articles/the-meaning-of-light-and-color 16. https://www.goodreads.com/quotes/811-for-instance-on-the-planet-earth-man-had-always-assumed 17. https://apod.nasa.gov/apod/ap211020.html 18. https://apod.nasa.gov/apod/archivepix.html 19. https://apod.nasa.gov/apod/lib/apsubmit2015.html 20. https://apod.nasa.gov/apod/lib/aptree.html 21. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search 22. https://apod.nasa.gov/apod/calendar/allyears.html 23. https://apod.nasa.gov/apod.rss 24. https://apod.nasa.gov/apod/lib/edlinks.html 25. https://apod.nasa.gov/apod/lib/about_apod.html 26. http://asterisk.apod.com/discuss_apod.php?date=211021 27. https://apod.nasa.gov/apod/ap211022.html 28. http://www.phy.mtu.edu/faculty/Nemiroff.html 29. http://www.phy.mtu.edu/ 30. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html 31. http://www.astro.umd.edu/ 32. https://apod.nasa.gov/apod/lib/about_apod.html#srapply 33. https://www.nasa.gov/about/highlights/HP_Privacy.html 34. https://astrophysics.gsfc.nasa.gov/ 35. https://www.nasa.gov/ 36. https://www.nasa.gov/centers/goddard/ 37. http://www.mtu.edu/