A group of researchers may have found the first indication of the so-called gravitational wave background and hopes to open a completely new window into the universe for us soon. The extremely difficult and not yet unequivocal detection was achieved within the framework of the North American Nanohertz Observatory for Gravitational Waves (NANOGrav).

Should the provisional result change confirm, astronomers would have a whole new way of studying the formation of supermassive black holes, as they are at the center of most galaxies.

A new era of astronomy This experiment also has its starting point in Albert Einstein’s general theory of relativity. According to her, gravity is a property of space that propagates at the speed of light. According to the theory, if massive bodies are accelerated, they generate gravitational waves that deform the structure of space – but only minimally even with large masses. Einstein himself therefore assumed that they would never be detectable. But that’s exactly what succeeded 2015 with the Ligo gravitational wave observatory in the USA and the search has now become almost routine. Almost 50 Gravitational waves have already been confirmed and allow a look at cosmic events that cannot be observed otherwise.

While Ligo – and now also Virgo – detect gravitational waves that arise from individual events such as a collision of black holes, NANOGrav has a different goal. The experiment is intended to look for clues to the innumerable and long overlapping gravitational waves that arose in the billions of years of history of our universe, for example through supermassive black holes orbiting each other. The researchers call this the “gravitational wave background” and use an observatory “the size of our galaxy” to find it, as the University of Boulder puts it.

Of course, the measuring devices are not nearly as big , but the description is not entirely out of thin air: For their analysis, the researchers examined the signals of several dozen pulsars that are distributed over the entire Milky Way. The researchers have taken advantage of the accuracy of these neutron stars, which emit regular pulses of radio waves with the precision of an atomic clock. Because gravitational waves distort these signals of the pulsars minimally and by comparing the galactic lighthouses, the researchers hope to find those gravitational waves that last not seconds, but years or decades and distort our universe as a background.

Representation of the pulsar signals that Arriving on earth distorted.

(Image: NANOGrav / T. Klein)

Exploring the “dark “Universe As the researchers now explain, they had been looking for deviations in the pulsar signals in the nanosecond range, which indicates that the position of the earth was minimally shifted by gravitational waves. Her hope was to find such slight shifts in the signals of some pulsars, explains study leader Joseph Simon. After all, these are deviations that are extremely difficult to prove. But when they looked at all of them, they actually found overlapping matches, and surprisingly strong ones. You could have ruled out many known sources of interference, but they are not yet absolutely certain. This would require more data and longer observations.

Should this provisional result be confirmed, another signal source would be available for research, with which it can explore “dark” objects in space. Using such gravitational waves, researchers could then, for example, study how the supermassive black holes are formed in the center of galaxies or how galaxies merge, according to NANOGrav. But it also states that the loss of the Arecibo radio telescope in Puerto Rico is a serious setback that will affect this research in the future. They have published their study in The Astrophysical Journal Letters.

(mho)