Today, Thursday, the detection, for the first time, of a background vibration of the cosmos from the merger of innumerable supermassive black holes has been announced. The discovery has been made by various centers for the detection of gravitational waves that, together, are grouped in the consortium called NANOGrav.
Gravitational waves are vibrations of space(time) generated by rapidly moving massive objects (as, for example, when pairs of black holes or neutron stars orbit around a common center of mass). These waves propagate through space at the speed of light, and when they reach Earth they are extremely weak, so their detection is very complex.
Until now, only gravitational waves created by specific events have been detected, such as those released just at the moment of the merger of two black holes or two neutron stars. But it was believed that the universe should be filled with a very weak background vibration, the result of the combination of a multitude of sources of gravitational waves, especially those generated by the merger of huge black holes, called supermassive and found in the center of the most galaxies.
Direct detection of this background vibration is not possible with current technology, as it is extremely weak. So the researchers have used an indirect method based on the study of pulsars, neutron stars that rotate at high speed while emitting beams of radiation in a very directional way.
As the pulsar spins, its radiation beams sweep through space, and if these emissions are focused toward Earth they can be picked up as pulsations (hence their name), similar to how light from a lighthouse is perceived. As the rotation of the pulsars is very regular, the radiation pulses that are received have such a precise cadence that they can be used as authentic clocks of the universe.
Oscillations in space caused by passing gravitational waves cause tiny irregularities in how pulsar signals reach our planet. That is, their heartbeats are advanced or delayed very slightly.
The discovery has been possible by studying, for 15 years, the signals of 67 pulsars. Although the main sources of gravitational waves that would have contributed to the existence of this background would be the mergers of supermassive black holes in the center of galaxies, the scientists do not rule out that there may also be contributions from other phenomena, such as the exponential expansion that it underwent. the universe in its first moments of life.
