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 the community has been waiting for for a while,” she said, adding that independent measurements from other pulsar timing collaborations reinforced the findings.
Still, said Dr. Soares-Santos, it was too early to say what impact a gravitational wave background might have on future research. If the signal really came from the slow, inward spirals of supermassive black holes, as many NANOGrav collaborators believe, it would reinforce what scientists understand about how early galaxies merged to form ever-larger systems of stars and dust that formed eventually settled in the complex structures observed today.
But if the ripples originated with the Big Bang, they could instead provide insight into the expansion of the cosmos or the nature of dark matter — the invisible glue scientists say holds the universe together — and maybe even new particles. or reveal powers that once existed. (Experts noted that the gravitational wave background could also come from multiple sources, in which case the challenge would be disentangling how much comes from where.)
The NANOGrav team is already analyzing all the data from gravitational wave collaborations around the world, equivalent to about 25 years of measurements from 115 pulsars. These results will be revealed in about a year, said Dr. Siemens, adding that he expected them to exceed the 5 sigma discovery level.
But it may take a few more years to confirm the source of the gravitational wave background. Researchers have already started using their data to compile maps of the universe and to look for intense, nearby regions of gravitational wave signals that point to an individual supermassive black hole binary. That’s where the fun begins, said Dr. Mingarelli, who looks forward to analyzing those maps and searching for even more exotic phenomena, such as galactic jets, cosmic strings or wormholes.
“This could lead to something very groundbreaking,” said Dr. Soares-Santos, who compared it to the discovery of the cosmic microwave background in the 1960s, which has since changed physicists’ understanding of the early universe. “We don’t know yet what impact it will have, but it will certainly be a new chapter in the book of gravitational waves. And it looks like we are watching this book being written.”
Dennis Overbye reporting contributed.
