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. 2025 January 17 [2]See Explanation. Clicking on the picture will download the highest resolution version available. Supernova Remnant Cassiopeia A Image Credit: [3]NASA, [4]ESA, [5]CSA, [6]STScI; D. Milisavljevic (Purdue University), T. Temim (Princeton University), I. De Looze (University of Gent) Explanation: [7]Massive stars in our Milky Way Galaxy live spectacular lives. Collapsing from vast cosmic clouds, their nuclear furnaces ignite and create heavy elements in their cores. After only a few million years for the most massive stars, the [8]enriched material is blasted back into interstellar space where star formation can begin anew. The expanding debris cloud known as Cassiopeia A is an example of this final phase of the [9]stellar life cycle. Light from the supernova explosion that created this remnant would have been first [10]seen in planet Earth's sky about 350 years ago, although it took that light 11,000 years to reach us. [11]This sharp NIRCam image from the James Webb Space Telescope shows the still hot filaments and knots in the supernova remnant. The whitish, smoke-like outer shell of the expanding blast wave is about 20 light-years across. A series of light echoes from the massive star's cataclysmic explosion are also [12]identified in Webb's detailed images of the surrounding interstellar medium. Tomorrow's picture: light-weekend __________________________________________________________________ [13]< | [14]Archive | [15]Submissions | [16]Index | [17]Search | [18]Calendar | [19]RSS | [20]Education | [21]About APOD | [22]Discuss | [23]> __________________________________________________________________ Authors & editors: [24]Robert Nemiroff ([25]MTU) & [26]Jerry Bonnell ([27]UMCP) NASA Official: Amber Straughn [28]Specific rights apply. [29]NASA Web Privacy Policy and Important Notices A service of: [30]ASD at [31]NASA / [32]GSFC, [33]NASA Science Activation & [34]Michigan Tech. U. References 1. https://apod.nasa.gov/apod/archivepix.html 2. https://apod.nasa.gov/apod/image/2501/CasA_nircam_4096.jpg 3. https://www.nasa.gov/ 4. https://www.esa.int/ 5. https://www.asc-csa.gc.ca/eng/ 6. https://www.stsci.edu/ 7. https://en.wikipedia.org/wiki/Stellar_evolution#Massive_stars 8. https://apod.nasa.gov/apod/ap190801.html 9. https://universe.nasa.gov/stars/basics/ 10. https://spider.seds.org/spider/Vars/casA.html 11. https://webbtelescope.org/contents/media/images/2023/149/01HGGZ4TPD8XFNPCBTZ2QYM0ZM 12. https://science.nasa.gov/missions/webb/nasas-webb-reveals-intricate-layers-of-interstellar-dust-gas/ 13. https://apod.nasa.gov/apod/ap250116.html 14. https://apod.nasa.gov/apod/archivepix.html 15. https://apod.nasa.gov/apod/lib/apsubmit2015.html 16. https://apod.nasa.gov/apod/lib/aptree.html 17. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search 18. https://apod.nasa.gov/apod/calendar/allyears.html 19. https://apod.nasa.gov/apod.rss 20. https://apod.nasa.gov/apod/lib/edlinks.html 21. https://apod.nasa.gov/apod/lib/about_apod.html 22. http://asterisk.apod.com/discuss_apod.php?date=250117 23. https://apod.nasa.gov/apod/ap250118.html 24. http://www.phy.mtu.edu/faculty/Nemiroff.html 25. http://www.phy.mtu.edu/ 26. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html 27. http://www.astro.umd.edu/ 28. https://apod.nasa.gov/apod/lib/about_apod.html#srapply 29. https://www.nasa.gov/about/highlights/HP_Privacy.html 30. https://astrophysics.gsfc.nasa.gov/ 31. https://www.nasa.gov/ 32. https://www.nasa.gov/centers/goddard/ 33. https://science.nasa.gov/learners 34. http://www.mtu.edu/