¿ 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 November 4 [2]See Explanation. Clicking on the picture will download the highest resolution version available. Fifty Gravitational Wave Events Illustrated Image Credit: [3]LIGO [4]Virgo Collaborations, Frank Elavsky, Aaron Geller, [5]Northwestern U. Explanation: Over fifty [6]gravitational wave events have now been detected. These events mark the distant, violent collisions of [7]two black holes, a black hole and a neutron star, or [8]two neutron stars. Most of the [9]50 events were detected in 2019 by the [10]LIGO gravitational wave detectors in the [11]USA and the [12]VIRGO detector in [13]Europe. In the [14]featured illustration summarizing the masses of the first [15]50 events, blue dots indicate higher-mass [16]black holes while orange dots denote lower-mass [17]neutron stars. Astrophysicists are [18]currently uncertain, though, about the [19]nature of events marked in white involving masses that appear to be in the middle -- between two and five solar masses. The [20]night sky in optical light is dominated by nearby and bright planets and stars that have been known since the dawn of humanity. In contrast, the [21]sky in gravitational waves is dominated by distant and dark [22]black holes that have only been known about for less than five years. This contrast is enlightening -- understanding the [23]gravitational wave sky is already reshaping humanity's knowledge not only of [24]star birth and death across the universe, but [25]properties of the universe itself. Tomorrow's picture: open space __________________________________________________________________ [26]< | [27]Archive | [28]Submissions | [29]Index | [30]Search | [31]Calendar | [32]RSS | [33]Education | [34]About APOD | [35]Discuss | [36]> __________________________________________________________________ Authors & editors: [37]Robert Nemiroff ([38]MTU) & [39]Jerry Bonnell ([40]UMCP) NASA Official: Phillip Newman [41]Specific rights apply. [42]NASA Web Privacy Policy and Important Notices A service of: [43]ASD at [44]NASA / [45]GSFC & [46]Michigan Tech. U. References 1. https://apod.nasa.gov/apod/archivepix.html 2. https://apod.nasa.gov/apod/image/2011/GWaveSources2020Oct_LigoVIrgo_2977.jpg 3. https://www.ligo.org/ 4. https://www.virgo-gw.eu/ 5. https://media.ligo.northwestern.edu/ 6. https://en.wikipedia.org/wiki/Gravitational_wave 7. https://apod.nasa.gov/apod/ap151020.html 8. https://apod.nasa.gov/apod/ap171016.html 9. https://www.ligo.org/science/Publication-O3aCatalog/ 10. https://apod.nasa.gov/apod/ap160207.html 11. https://en.wikipedia.org/wiki/United_States 12. https://www.virgo-gw.eu/ 13. https://en.wikipedia.org/wiki/Europe 14. https://www.ligo.org/science/Publication-O3aCatalog/images/Stellar_Graveyard_noerror_GWonly.png 15. https://www.aei.mpg.de/549420/dozens-of-new-gravitational-wave-events-in-six-months 16. https://www.nasa.gov/audience/forstudents/k-4/stories/nasa-knows/what-is-a-black-hole-k4.html 17. https://imagine.gsfc.nasa.gov/science/objects/neutron_stars1.html 18. https://img1.wsimg.com/isteam/ip/f9769a59-a6b9-4e5e-8893-3ca270b404ce/EA145108-1AC0-4755-A73A-836CFD6EA571.jpeg 19. https://apod.nasa.gov/apod/ap200908.html 20. https://apod.nasa.gov/apod/ap201021.html 21. https://apod.nasa.gov/apod/ap170928.html 22. https://en.wikipedia.org/wiki/Black_hole 23. https://youtu.be/iphcyNWFD10 24. https://science.nasa.gov/astrophysics/focus-areas/how-do-stars-form-and-evolve 25. https://arxiv.org/abs/1908.06060 26. https://apod.nasa.gov/apod/ap201103.html 27. https://apod.nasa.gov/apod/archivepix.html 28. https://apod.nasa.gov/apod/lib/apsubmit2015.html 29. https://apod.nasa.gov/apod/lib/aptree.html 30. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search 31. https://apod.nasa.gov/apod/calendar/allyears.html 32. https://apod.nasa.gov/apod.rss 33. https://apod.nasa.gov/apod/lib/edlinks.html 34. https://apod.nasa.gov/apod/lib/about_apod.html 35. http://asterisk.apod.com/discuss_apod.php?date=201104 36. https://apod.nasa.gov/apod/ap201105.html 37. http://www.phy.mtu.edu/faculty/Nemiroff.html 38. http://www.phy.mtu.edu/ 39. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html 40. http://www.astro.umd.edu/ 41. https://apod.nasa.gov/apod/lib/about_apod.html#srapply 42. https://www.nasa.gov/about/highlights/HP_Privacy.html 43. https://astrophysics.gsfc.nasa.gov/ 44. https://www.nasa.gov/ 45. https://www.nasa.gov/centers/goddard/ 46. http://www.mtu.edu/