Marcelle Soares-Santos, an astrophysicist at the University of Michigan who was not involved in the work, acknowledged that while this was early evidence, the results were enticing. “This is something that the community has been anticipating for quite a while,” she said, adding that independent measurements from other pulsar timing collaborations strengthened the findings.
Still, Dr. Soares-Santos said, it was too soon to tell what impact a gravitational-wave background might have on future research. If the signal really was from the slow, inward spiraling of supermassive black holes, as many NANOGrav collaborators believe, it would augment what scientists understand about the way early galaxies merged, forming ever-larger systems of stars and dust that eventually settled into the complex structures observed today.
But if the ripples originated with the Big Bang, they might instead provide insight into the expansion of the cosmos or the nature of dark matter — the invisible glue scientists think holds the universe together — and perhaps even reveal new particles or forces that once existed. (Experts noted that the gravitational-wave background could also originate from multiple sources, in which case the challenge would be to disentangle how much comes from where.)
The NANOGrav team is already working on analyzing all the data from gravitational-wave collaborations around the world, equaling around 25 years’ worth of measurements from 115 pulsars. These results will be unveiled in a year or so, Dr. Siemens said, adding that he expected them to exceed the 5-sigma discovery level.
But a few more years may be needed to confirm the source of the gravitational-wave background. Researchers have already begun using their data to piece together maps of the universe and to look for intense, nearby regions of gravitational-wave signals indicative of an individual supermassive black hole binary. That’s where the fun starts, said Dr. Mingarelli, who is looking forward to analyzing those maps and searching for even more exotic phenomena, like galactic jets, cosmic strings or wormholes.
“This could lead to something really groundbreaking,” Dr. Soares-Santos said, comparing it to the discovery of the cosmic microwave background in the 1960s, which has since transformed physicists’ knowledge about the early universe. “We don’t know yet what impact it will have, but it will definitely be a new chapter in the book of gravitational waves. And it looks like we are watching this book be written.”
Dennis Overbye contributed reporting.