11 GW190521 Massive Merger Art Annotated (IMAGE) Northwestern University Caption Artist concept illustrating a hierarchical scheme for merging black holes. LIGO and Virgo recently observed a black hole merger with a final mass of 142 times that of the sun, making it the largest of its kind observed in gravitational waves to date. The event is thought to have occurred when two black holes of about 66 and 85 solar masses spiraled into each other and coalesced. Theoretical models indicate that nature is not likely to form black holes of this heft; in particular, models identify a range of masses between 65 and 120 solar masses, called the "pair-instability mass gap," in which it is thought that black holes cannot be formed by a collapsing star. So how did the two merging black holes observed by LIGO and Virgo originate? Scientists think that these black holes may have themselves formed from the earlier mergers of two smaller black holes, as indicated in the illustration. Credit LIGO/Caltech/MIT/R. Hurt (IPAC) Usage Restrictions Credit must be given License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.