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. 2019 September 6 [2]See Explanation. Clicking on the picture will download the highest resolution version available. Recycling Cassiopeia A Image Credit: X-ray - [3]NASA, [4]CXC, SAO; Optical - [5]NASA,STScI Explanation: 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 a few million years, the [6]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 stellar life cycle. Light from the explosion which created this supernova remnant would have been first [7]seen in planet Earth's sky about 350 years ago, although it took that light about 11,000 years to reach us. [8]This false-color image, composed of X-ray and optical image data from the Chandra X-ray Observatory and Hubble Space Telescope, shows the still hot filaments and knots in the remnant. [9]It spans about 30 light-years at the estimated distance of Cassiopeia A. High-energy X-ray emission from specific elements has been color coded, silicon in red, sulfur in yellow, calcium in green and iron in purple, to help [10]astronomers explore the recycling of our galaxy's [11]star stuff. Still expanding, the outer blast wave is seen in blue hues. [12]The bright speck near the center is a neutron star, the incredibly dense, collapsed remains of the massive stellar core. Tomorrow's picture: Wolf's dusty cave __________________________________________________________________ [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: Phillip Newman [28]Specific rights apply. [29]NASA Web Privacy Policy and Important Notices A service of: [30]ASD at [31]NASA / [32]GSFC & [33]Michigan Tech. U. References 1. https://apod.nasa.gov/apod/archivepix.html 2. https://apod.nasa.gov/apod/image/1909/Chandrafirstlight_0.jpg 3. https://www.nasa.gov/ 4. http://chandra.harvard.edu/ 5. http://www.stsci.edu/ 6. https://apod.nasa.gov/apod/ap190801.html 7. http://spider.seds.org/spider/Vars/casA.html 8. https://chandra.harvard.edu/photo/2019/firstlight/ 9. https://chandra.harvard.edu/photo/2009/casa2/ 10. https://arxiv.org/abs/1111.7316 11. https://apod.nasa.gov/apod/ap171119.html 12. https://apod.nasa.gov/apod/ap170501.html 13. https://apod.nasa.gov/apod/ap190905.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=190906 23. https://apod.nasa.gov/apod/ap190907.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. http://www.mtu.edu/