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 March 26 [2]See Explanation. Clicking on the picture will download the highest resolution version available. The Medusa Nebula Image Credit & [3]Copyright: [4]Josep Drudis Explanation: Braided and serpentine filaments of glowing gas suggest this nebula's popular name, The Medusa Nebula. Also known as Abell 21, this Medusa is an old [5]planetary nebula some 1,500 light-years away in the constellation Gemini. Like its [6]mythological namesake, the nebula is associated with a dramatic transformation. The [7]planetary nebula phase represents a final stage in [8]the evolution of low mass stars like the sun as they transform themselves from [9]red giants to hot white dwarf stars and in the process shrug off their outer layers. Ultraviolet [10]radiation from the hot star powers the nebular glow. The Medusa's transforming star is the faint one near the center of the overall bright crescent shape. In [11]this deep telescopic view, fainter filaments clearly extend above and right of the bright crescent region. The Medusa Nebula is estimated to be over 4 light-years across. Tomorrow's picture: light weekend __________________________________________________________________ [12]< | [13]Archive | [14]Submissions | [15]Index | [16]Search | [17]Calendar | [18]RSS | [19]Education | [20]About APOD | [21]Discuss | [22]> __________________________________________________________________ Authors & editors: [23]Robert Nemiroff ([24]MTU) & [25]Jerry Bonnell ([26]UMCP) NASA Official: Phillip Newman [27]Specific rights apply. [28]NASA Web Privacy Policy and Important Notices A service of: [29]ASD at [30]NASA / [31]GSFC & [32]Michigan Tech. U. References 1. https://apod.nasa.gov/apod/archivepix.html 2. https://apod.nasa.gov/apod/image/2103/Abell21-Drudis.jpg 3. https://apod.nasa.gov/apod/lib/about_apod.html#srapply 4. http://www.astrodrudis.com/ 5. https://www.messier.seds.org/planetar.html 6. http://en.wikipedia.org/wiki/Medusa 7. http://www.noao.edu/jacoby/pn_gallery.html 8. http://casswww.ucsd.edu/public/tutorial/StevI.html 9. http://en.wikipedia.org/wiki/Red_giant 10. http://hyperphysics.phy-astr.gsu.edu/hbase/ems1.html 11. https://astrodrudis.com/abell-21-medusa-nebula/ 12. https://apod.nasa.gov/apod/ap210325.html 13. https://apod.nasa.gov/apod/archivepix.html 14. https://apod.nasa.gov/apod/lib/apsubmit2015.html 15. https://apod.nasa.gov/apod/lib/aptree.html 16. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search 17. https://apod.nasa.gov/apod/calendar/allyears.html 18. https://apod.nasa.gov/apod.rss 19. https://apod.nasa.gov/apod/lib/edlinks.html 20. https://apod.nasa.gov/apod/lib/about_apod.html 21. http://asterisk.apod.com/discuss_apod.php?date=210326 22. https://apod.nasa.gov/apod/ap210327.html 23. http://www.phy.mtu.edu/faculty/Nemiroff.html 24. http://www.phy.mtu.edu/ 25. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html 26. http://www.astro.umd.edu/ 27. https://apod.nasa.gov/apod/lib/about_apod.html#srapply 28. https://www.nasa.gov/about/highlights/HP_Privacy.html 29. https://astrophysics.gsfc.nasa.gov/ 30. https://www.nasa.gov/ 31. https://www.nasa.gov/centers/goddard/ 32. http://www.mtu.edu/