Scientists have announced that they have recorded a signal unlike any gravitational wave signal they have recorded before. The team recorded the signal from a gravitational wave resulting from a binary black hole merger where the black holes had unequal masses. According to the team, the binary black hole merger was a result of two black holes of approximately eight and 30 times the mass of the Sun merging.
The signal is called GW190412 and was captured using the LIGO and Virgo detectors. The team says for the very first time that they have been able to hear in GW190412 the unmistakable gravitational-wave hum, a higher harmonic, similar to overtones of musical instruments. The team says in this new observation, the overtones in the gravitational-wave signal are much louder than usual observations.
The scientists can hear the tone for the first time because of how much louder they are in the GW190412 signal. The team says the significant mass difference between the two black holes allows them to more precisely measure some properties of the system, including the distance from us, the angle we’re seeing them at, and how fast the heavy black hole is spinning on its axis. GW190412 was observed by both the LIGO and Virgo detector on April 12, 2019.
The analysis revealed that the black hole merger happened at a distance of 1.9 to 2.9 billion light-years from Earth. Scientists are so excited by the signals produced from the merger because all previously observed binaries consisted of black holes of roughly the same mass. The unequal masses imprint themselves on the observed gravitational-wave signal, allowing scientists to measure some astrophysical properties of the system more precisely.
The scientists also used GW190412 to look for deviations of the signals from what Einstein’s general theory of relativity predicts. The team says even though the signal had properties unlike others found so far, the researchers found no significant departure from the general-relativistic predictions.