Possible Detection of Merging Supermassive Black Holes by Astronomers.

The NANOGrav project has proposed a new method to observe the mergers of supermassive black holes by studying the radio pulses of millisecond pulsars. By observing the overall statistical shifts of lots of pulsars, they can detect the large-scale effect of the gravitational waves from merging supermassive black holes. Although the idea is not without its challenges, the study puts some upper constraints on gravitational wave observations and shows that there has not been any billion-solar-mass black hole merger within 300 million light years. With further observations, they will be able to observe million-solar-mass black hole mergers in that range, or billion-solar-mass ones at greater distances.