Source / Author: LIGO CalTech

Summary: The third observing run (O3) of LIGO and Virgo has provided new insights into binary black hole (BBH) systems, particularly during their late inspiral and merger phases. Since the first detection of a BBH merger, GW150914, in 2015, most observed events have involved black holes of nearly equal masses. This trend was broken with the observation of GW190412 on April 12, 2019, which involved a BBH system with significantly unequal masses—one black hole being 30 times the mass of the sun and the other 8 times. This event, detected by Advanced Virgo and two Advanced LIGO detectors, showed higher harmonics in the gravitational-wave signal for the first time. These harmonics helped constrain the inclination of the BBH system’s orbital plane and measure the distance of the source more accurately. The findings also confirmed the predictions of Einstein’s theory of general relativity. Frank Ohme, a LIGO scientist, emphasized that this discovery opens new opportunities to understand BBH systems and test general relativity in new ways.

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