The NANOGrav team can essentially turn the Milky Way into a giant gravitational wave detector by measuring signals from these pulsars to determine when a wave hits them. The collision of giant black holes—or some other extremely energetic process—generates gravitational waves that always squeeze and stretch space-time extremely lightly, adjusting the time interval between flashes of the pulsar. NANOGrav researchers measured those microscopic changes between 68 pulsars, then compared them with each other, finding a pattern that is likely indicative of low-frequency gravitational waves. Other collaborative groups do the same with separate sets of pulsars.
The teams have spent more than a decade collecting and analyzing data to reduce the uncertainty of the measurement and to be sure they have detected the real signature of gravitational waves and not some phenomenon. other universes or mere noise. The NANOGrav team, consisting of nearly 200 people, conducted statistical analysis and found less than one in a thousandth the odds that the signal they observed could happen by chance. Other collaborators found similar levels of statistical significance.
While this is most likely a sign of real gravitational waves from massive black holes, the teams are still reluctant to use the word “detection” to describe their findings. Nine years ago, the US-based BICEP2 collaboration, using an Antarctic telescope, claimed to have detected primordial gravitational waves coming from the big bang, only to discover that the signal of they really come from troublesome dust in the Milky Way—and that has led the researchers to be cautious about their conclusions. “The gravitational wave community is very wary of things like this,” said Scott Ransom, an astronomer with the National Radio Astronomy Observatory and former president of NANOGrav.
For their measurements, the NANOGrav team used several radio telescopes: the Green Bank Observatory in West Virginia, the Very Large Array in New Mexico, and the giant Arecibo Observatory in Puerto Rico, an instrument Iconic collapse in 2020. Other teams use radio telescopes in five countries in Europe, India, China and Australia. Many telescopes have recently joined this effort, including CHIME in Canada and MeerTime in South Africa.
Ransom said the collaboration between scientists in the US and China is remarkable. While a controversial 2011 law called wolf revision prohibiting NASA from working directly with Chinese entities because of security concerns, such restrictions do not apply to National Science Foundation-funded efforts such as NANOGrav. “Politics has made some of our cooperation difficult,” Ransom said. “We have to find a way to work together, because science is definitely better when we do it. It’s terrible to be thwarted by politics.”
The groups work together through a type of hypercollaboration known as the International Pulse Time Array. Although the team’s geographical distance makes it difficult for scientists to communicate across time zones, they can combine their data sets, improving the accuracy and reliability of their calculations. their measurement. Michael Keith, an astrophysicist on the executive committee of the European Pulsar Time Array, wrote in an email to WIRED: “One cannot build a galaxy-sized gravitational-wave telescope in your backyard. . “It takes the combined effort of hundreds of astronomers, theorists, engineers and managers to study the universe at this scale.”
