¿ 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. 2020 September 8 [2]See Explanation. Clicking on the picture will download the highest resolution version available. GW190521: Unexpected Black Holes Collide Illustration Credit: [3]Raúl Rubio ([4]Virgo Valencia Group, [5]The Virgo Collaboration) Explanation: How do black holes like this form? The two black holes that spiraled together to produce the gravitational wave event [6]GW190521 were not only the [7]most massive black holes ever seen by [8]LIGO and [9]VIRGO so far, their masses -- 66 and 85 solar masses -- were unprecedented and unexpected. Lower mass black holes, below about 65 solar masses are known to form in [10]supernova explosions. Conversely, higher mass black holes, above about 135 solar masses, are thought to be created by [11]very massive stars imploding after they use up their weight-bearing nuclear-fusion-producing [12]elements. How such [13]intermediate mass black holes came to exist is yet unknown, although one hypothesis holds that they result from consecutive collisions of stars and black holes in dense star clusters. [14]Featured is an illustration of the black holes just before collision, annotated with arrows indicating their spin axes. In the illustration, the spiral waves indicate the production of [15]gravitational radiation, while the surrounding stars highlight the possibility that [16]the merger occurred in a [17]star cluster. Seen last year but emanating from an epoch when the universe was only about half its present age ([18]z ~ 0.8), black hole merger [19]GW190521 is the farthest yet detected, to within measurement errors. Astrophysicists: [20]Browse 2,200+ codes in the Astrophysics Source Code Library Tomorrow's picture: stellar sisters __________________________________________________________________ [21]< | [22]Archive | [23]Submissions | [24]Index | [25]Search | [26]Calendar | [27]RSS | [28]Education | [29]About APOD | [30]Discuss | [31]> __________________________________________________________________ Authors & editors: [32]Robert Nemiroff ([33]MTU) & [34]Jerry Bonnell ([35]UMCP) NASA Official: Phillip Newman [36]Specific rights apply. [37]NASA Web Privacy Policy and Important Notices A service of: [38]ASD at [39]NASA / [40]GSFC & [41]Michigan Tech. U. References 1. https://apod.nasa.gov/apod/archivepix.html 2. https://apod.nasa.gov/apod/image/2009/GW190521_Virgo_1667.jpg 3. https://fsi.ucf.edu/2020/04/30/interview-with-fsis-senior-postdoctoral-researcher-dr-raul-carballo-rubio/ 4. https://www.uv.es/virgogroup/index.html 5. https://www.virgo-gw.eu/ 6. https://youtu.be/hpbmi8oPipY 7. https://en.wikipedia.org/wiki/List_of_gravitational_wave_observations 8. https://www.ligo.caltech.edu/ 9. https://www.virgo-gw.eu/ 10. https://apod.nasa.gov/apod/ap171016.html 11. https://apod.nasa.gov/apod/ap170606.html 12. https://apod.nasa.gov/apod/ap200809.html 13. https://cplberry.com/2020/09/02/gw190521-the-big-one/ 14. https://www.ligo.org/detections/GW190521.php 15. https://spaceplace.nasa.gov/gravitational-waves/en/ 16. https://apod.nasa.gov/apod/ap190414.html 17. https://apod.nasa.gov/apod/ap190404.html 18. https://apod.nasa.gov/apod/ap130408.html 19. https://en.wikipedia.org/wiki/GW190521 20. http://ascl.net/ 21. https://apod.nasa.gov/apod/ap200907.html 22. https://apod.nasa.gov/apod/archivepix.html 23. https://apod.nasa.gov/apod/lib/apsubmit2015.html 24. https://apod.nasa.gov/apod/lib/aptree.html 25. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search 26. https://apod.nasa.gov/apod/calendar/allyears.html 27. https://apod.nasa.gov/apod.rss 28. https://apod.nasa.gov/apod/lib/edlinks.html 29. https://apod.nasa.gov/apod/lib/about_apod.html 30. http://asterisk.apod.com/discuss_apod.php?date=200908 31. https://apod.nasa.gov/apod/ap200909.html 32. http://www.phy.mtu.edu/faculty/Nemiroff.html 33. http://www.phy.mtu.edu/ 34. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html 35. http://www.astro.umd.edu/ 36. https://apod.nasa.gov/apod/lib/about_apod.html#srapply 37. https://www.nasa.gov/about/highlights/HP_Privacy.html 38. https://astrophysics.gsfc.nasa.gov/ 39. https://www.nasa.gov/ 40. https://www.nasa.gov/centers/goddard/ 41. http://www.mtu.edu/