MSU scientists have discovered the gravitational “noise” of the universe

Director of the Institute Sternberg: “This day entered the history of modern fundamental science”

Gravitational “noise” – low-frequency waves that are born in different parts of the universe due to the merger of supermassive black holes, were discovered by employees of Moscow State University. Lomonosov as part of an international group of scientists. They were helped in this by the so-called “space clock” – rapidly rotating neutron stars.

Gravitational waves are changes in the gravitational field that propagate like waves. Their existence was predicted in 1916 by Albert Einstein, and was first discovered on September 14, 2015 at the LIGO (Laser-Interferometric Gravitational-Wave Observatory) installations by members of an international group representing 15 countries.

Unlike those previously discovered gravitational waves that propagate from a specific point in the Universe, the newly discovered low-frequency gravitational waves are a weak “noise” of space-time that comes to Earth from many sources, from different directions.

To register such a signal in the nanohertz frequency range, scientists did not need to build a large LIGO-type detector, more than 3 kilometers long. According to one of the authors of the discovery, director of the State Astronomical Institute. Sternberg of Moscow State University, Corresponding Member of the Russian Academy of Sciences Konstantin Postnov, he and his colleagues managed to find traces of such a weak “whisper of the Universe” in the signal from the “space clock” – radio pulsars. These are rapidly rotating neutron stars that have been observed by radio astronomers since 1967.

“The first such method of detecting a background of gravitational waves was proposed back in 1978 by Mikhail Vasilyevich Sazhin, an employee of the SAI MGU,” notes Postnov. – In order to prove that his theory of registration of gravitational waves is correct, it took us all several decades of regular tracking of the arrival times of impulses from several tens of millisecond radio pulsars, very stable “cosmic clocks”.

They were called “hours” for a stable “move” – ​​rotation, the speed of which changes only under the influence of specific factors. In particular, a gravitational perturbation that arose due to the merger of two black holes in the region of this radio pulsar can lead to a temporary change in the speed of rotation of the body. A number of researchers also assume that the background of gravitational waves is of a cosmological nature. That is, it is taken as a trace of physical processes occurring in the Universe in the distant past.

The first case of detecting gravitational “noise” was recorded by astrophysicists on June 29, 2023.

“This day went down in the history of modern fundamental science as the day of the discovery of the stochastic background of low-frequency gravitational waves,” says Konstantin Postnov.

The work, according to him, was carried out by a whole network of world radio antennas in Europe, the USA, Australia and China, hundreds of astronomers took part in it.