On May 21, 2019 the Advanced LIGO detectors at Hanford and Livingston in the USA and the Virgo detector in Italy, observed a gravitational wave signal from the heaviest merger of black holes, yet observed.

The merging black holes being roughly 85 and 66 times as heavy as our sun, are among the heaviest ones seen yet. The LIGO group at PSU played a significant role in the observation of this very short and difficult to detect signal which lasted for about one tenth of a second. The remnant produced by the merger is as heavy as about 142 times the mass of our sun which places it in the category of intermediate-mass black holes, an elusive type of heavy black holes that had not been observed directly so far. Being heavier than the black holes observed which have masses comparable to our sun, but less heavy than the supermassive black holes that occupy the centres of galaxies, these intermediate-mass black holes and their formation methods are not well understood by astrophysicists. In fact this discovery is also unusual because it questions existing astrophysical models of black hole formation and stands to open new doors in our understanding of these objects.