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 December 7 [2]The featured image shows spectrograms for the first 90 gravitational wave events ever detected. Please see the explanation for more detailed information. Ninety Gravitational Wave Spectrograms and Counting Image Credit: [3]NSF, [4]LIGO, [5]VIRGO, [6]KAGRA, [7]Georgia Tech, [8]Vanderbilt U.; Graphic : [9]Sudarshan Ghonge & [10]Karan Jani Explanation: Every time two massive [11]black holes collide, a loud chirping sound is broadcast out into the universe in [12]gravitational waves. Humanity has only had the technology to hear [13]these unusual chirps for the past seven years, but since then we have heard about 90 -- during the first three observing runs. [14]Featured above are the spectrograms -- plots of gravitational-wave frequency versus time -- of these 90 as detected by the giant detectors of [15]LIGO (in the [16]USA), [17]VIRGO (in [18]Europe), and [19]KAGRA (in [20]Japan). The more [21]energy received on [22]Earth from a collision, the [23]brighter it appears on the graphic. Among many [24]science firsts, these [25]gravitational-radiation chirps are giving humanity an unprecedented [26]inventory of black holes and neutron stars, and a new way to [27]measure the expansion rate of our universe. A [28]fourth gravitational wave observing run with increased sensitivity is currently planned to begin in 2022 December. Tomorrow's picture: comet tails __________________________________________________________________ [29]< | [30]Archive | [31]Submissions | [32]Index | [33]Search | [34]Calendar | [35]RSS | [36]Education | [37]About APOD | [38]Discuss | [39]> __________________________________________________________________ Authors & editors: [40]Robert Nemiroff ([41]MTU) & [42]Jerry Bonnell ([43]UMCP) NASA Official: Phillip Newman [44]Specific rights apply. [45]NASA Web Privacy Policy and Important Notices A service of: [46]ASD at [47]NASA / [48]GSFC & [49]Michigan Tech. U. References 1. https://apod.nasa.gov/apod/archivepix.html 2. https://apod.nasa.gov/apod/image/2112/GWaveCatalog_LigoVirgo_5692.jpg 3. https://www.nsf.gov/ 4. https://www.ligo.org/about.php 5. http://public.virgo-gw.eu/the-virgo-collaboration/ 6. https://gwcenter.icrr.u-tokyo.ac.jp/en/organization 7. https://physics.gatech.edu/ 8. https://as.vanderbilt.edu/physics/ 9. https://humansofligo.blogspot.com/2019/05/sudarshan-ghonge.html 10. https://www.karanjani.com/ 11. https://apod.nasa.gov/apod/ap190414.html 12. https://spaceplace.nasa.gov/gravitational-waves/en/ 13. https://www.ligo.caltech.edu/video/ligo20160211v2 14. https://dcc.ligo.org/LIGO-G2102338/public 15. https://youtu.be/PVNlPUcPlB0 16. https://en.wikipedia.org/wiki/United_States 17. http://public.virgo-gw.eu/virgo-in-a-nutshell/ 18. https://en.wikipedia.org/wiki/Europe 19. https://gwcenter.icrr.u-tokyo.ac.jp/en/kagra-gallery 20. https://en.wikipedia.org/wiki/Japan 21. https://apod.nasa.gov/apod/ap171016.html 22. https://www.nasa.gov/topics/earth/index.html 23. https://i.pinimg.com/550x/81/21/c0/8121c0291fa14d1fe52b9eb007741cac.jpg 24. https://arxiv.org/abs/2111.03606 25. https://youtu.be/jtp71NT0GNg 26. https://www.ligo.org/science/Publication-O3bAstroDist/ 27. https://www.ligo.org/science/Publication-O3Cosmology/ 28. https://www.ligo.org/scientists/GWEMalerts.php 29. https://apod.nasa.gov/apod/ap211206.html 30. https://apod.nasa.gov/apod/archivepix.html 31. https://apod.nasa.gov/apod/lib/apsubmit2015.html 32. https://apod.nasa.gov/apod/lib/aptree.html 33. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search 34. https://apod.nasa.gov/apod/calendar/allyears.html 35. https://apod.nasa.gov/apod.rss 36. https://apod.nasa.gov/apod/lib/edlinks.html 37. https://apod.nasa.gov/apod/lib/about_apod.html 38. http://asterisk.apod.com/discuss_apod.php?date=211207 39. https://apod.nasa.gov/apod/ap211208.html 40. http://www.phy.mtu.edu/faculty/Nemiroff.html 41. http://www.phy.mtu.edu/ 42. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html 43. http://www.astro.umd.edu/ 44. https://apod.nasa.gov/apod/lib/about_apod.html#srapply 45. https://www.nasa.gov/about/highlights/HP_Privacy.html 46. https://astrophysics.gsfc.nasa.gov/ 47. https://www.nasa.gov/ 48. https://www.nasa.gov/centers/goddard/ 49. http://www.mtu.edu/