MOSCOW, June 29 An international scientific consortium showed that space-time is crumpled by giant gravitational waves generated by the merger of supermassive black holes.
Astronomers have for the first time presented experimental evidence of very long gravitational waves crushing outer space. They were recorded by ground-based radio telescopes that observe pulsars in many countries of the world. Four international consortiums at once published articles (here, here and here) about this on the scientific preprint server Arxiv.org.
According to Einstein's theory of relativity, gravitational waves are emitted by any object moving with acceleration. The more massive the object and the higher the speed, the more noticeable they are. The gravitational interaction is very weak compared to the electromagnetic one, it does not have a particle carrier, so many doubted that it could ever be registered.
Scientists assumed that powerful gravitational waves should come from very massive cosmic bodies, such as pairs of black holes, double neutron stars, white dwarfs. If you build very sensitive detectors, you might be able to catch something.
Ground-based gravitational wave detectors began to be built in the middle of the 20th century. It wasn't until 2015 that scientists from the LIGO collaboration reported their first successes. Short gravitational waves have been recorded from the merger of black holes with a mass of several of our suns. Now, gravitational waves, in fact, have been rediscovered, but in a completely different way — using pulsar timing.
Astronomers call pulsars neutron stars with a strong magnetic field that constantly emit streams of electromagnetic radiation. The energy flows are so powerful that after millions of light years, their traces are observed on Earth. The most amazing property of pulsars is their strict periodicity.
Scientists have suggested that if the object's pulsation deviates from the norm, then this could mean the impact on the Earth, and hence our radio detectors, of a gravitational wave. To confirm this, we need to observe quite a lot of pulsars and at the same time fix their anomalous behavior.
In 2016, scientists at NASA's Jet Propulsion Laboratory in Pasadena (USA) theoretically showed that operational observatories and instruments would be able to detect deviations in pulsations if the gravitational wave was very long. Such are born during the merger of supermassive black holes in colliding galaxies.
Several scientific collaborations in the world, including the Chinese FAST radio telescope and the «North American nanohertz gravitational wave observatory» NANOGrav, have joined the synchronous search for ultralong gravitational waves.
«Half of the galaxy acted as a detector for us,» NANOGrav notes. The scientists of this project monitored pulsations from nearly 70 objects, looking for delays in signal arrival due to the effects of a gravitational wave. These are very precise observations that require you to know where the center of mass of the solar system is to within a hundred meters. The observations took 15 years.
The authors of the work believe that long gravitational waves are caused by a pair of incompletely merged black holes weighing several million suns. They move in a 15-year orbit, gradually approaching each other. This causes them to lose energy, which ripples through space-time. Reaching the Earth, the wave causes it to toss and turn slightly, which is fixed by detectors that observe pulsars.
The authors of the work emphasize that the accuracy of this result is four sigma, that is, they are slightly contradictory, since in physics it is customary to consider a result with an accuracy of five sigma as a discovery . However, according to calculations, there is one chance in a thousand that the anomalies in pulsations are random, so the authors hope to confirm their data in the future.