Blazar series: merging of black holes will help to measure the universe more accurately

Russian scientists have developed a technique for studying systems of binary supermassive black holes, objects that form when galaxies merge. The proposed method will make it possible to calculate their mass, the size of the orbits, the speed of movement, reserves and losses of energy, as well as the life remaining before the merger. Black holes at the moment of convergence are a powerful source of gravitational waves. They, in turn, represent a channel of information, the development of which, in particular, will allow us to reliably measure the expansion of the Universe, understand the nature of space-time and create ultra-precise measuring instruments of a new generation.

How to find binary black holes

Most galaxies, including the Milky Way, have supermassive black holes at their centers. These are objects with masses ranging from hundreds of thousands to billions of solar masses. When galaxies merge, they form binary systems that emit powerful gravitational waves — ripples of space-time, experts from the Crimean Astrophysical Observatory of the Russian Academy of Sciences said.

They have developed a methodology that allows us to study the internal structure of such systems. This includes calculating the masses of the components, the sizes of their orbits, the speeds of movement, energy reserves and its losses due to gravitational radiation, as well as the lifetime of the system before unification. At the same time, experts have identified the main source of the powerful energy release that occurs as a result of the interaction of black holes.

RT-22 Radio telescope of the Simeiz Observatory

Photo: RIA Novosti/Anton Denisov

— The new method is based on data from long-term observation of five blazars. They were studied using the RT-22 22-meter radio telescope in Simeiz (Crimea). The history of continuous monitoring exceeds 50 years. The analysis of the information accumulated during this time makes it possible to draw reliable conclusions about the properties of space objects. In particular, the researchers have identified a class of objects with a special frequency of radiation. Simulations have shown that all five blazars are systems of paired supermassive black holes, and the periodicity may be related to their orbital motion at the stage of fusion," Alexander Volvach, Deputy director of the Russian Academy of Sciences, told Izvestia.

The particles in such a stream accelerate to speeds close to light. Moreover, the blazar jet is directed towards the Earth, so observers see it as an extremely bright source in the entire electromagnetic spectrum of radiation, the scientist said.

Why it is important to study active galactic nuclei

According to Alexander Volvach, about 150 objects have now been identified that claim to be binary supermassive black holes. Studying them allows us to gain new information about the universe.

Photo: Global Look Press/Cover Images

— In their normal state, these objects are extremely silent. They do not emit light and do not manifest themselves directly. Everything we know about them is through indirect effects, such as how they bend space, affect the movement of stars, and create jets. But during the merger, especially at the final stage, they literally "go on stage," the specialist explained.

It is at this moment, he said, that events of colossal power occur. Among other things, gravitational waves and vibrations arise, which carry information about both the binary system itself and how the fabric of space-time in its vicinity is arranged. Figuratively speaking, at the moment of fusion, black holes really begin to "talk".

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For example, the scientist said, the proposed model helped clarify the nature of the energy that results from this process. According to the findings, powerful bursts of radiation occur when a companion passes through the accretion disk (clusters of matter that, rotating, falls on a massive object) of the central black hole. According to the calculations made, with each such event, bursts can reach ~ 10⁴⁷ erg/s (hundreds of millions of times brighter than the Sun), which is completely consistent with observations.

Map of the Universe

Photo: Global Look Press/NASA

In general, Alexander Volvach added, binary systems of supermassive black holes are a powerful source of gravitational waves, which in turn represent a channel of information. Mastering it is the key to astronomy, which will significantly expand our knowledge of the universe, make it possible to clarify its dimensions, and also make it possible to create ultra—precise next-generation instruments.

In particular, with their help, specialists will be able to measure materials with atomic accuracy, calibrate length and time standards, as well as monitor tectonic shifts in the earth's crust and predict earthquakes. At the same time, quantum gravimeters based on gravitational field anomalies will help to find minerals on Earth and other planets.

— Black holes, for the most part, remain mathematical objects, convenient for explaining phenomena. Therefore, in order to better understand the physics of our universe, we must study them. However, most space objects are paired systems. These are both stars and groups of galaxies, so there is every reason to assume double nuclei in the centers of active galaxies," said Valery Vlasyuk, head of the scientific department of the Special Astrophysical Observatory of the Russian Academy of Sciences.

This is a convenient model to explain the quasi-periodic variability of radiation, he added. Therefore, the research of Crimean specialists is important. To complete the data, the study of radio waves should be supplemented with observations in other ranges of electromagnetic radiation — in visible light, as well as in hard gamma and X-ray radiation.

Photo: Global Look Press/Caltech/NASA

— Detecting a periodic signal is a key moment for confirming the existence of binary black holes, but none of the candidates for this role has been definitively confirmed, as there are alternative hypotheses. This underscores the need for a careful approach to data interpretation," said Sergey Sazonov, Head of the Laboratory of Experimental Astrophysics at the Space Research Institute of the Russian Academy of Sciences.

According to him, from the point of view of theory, binary supermassive black holes are an important part of the evolution of galaxies, which can merge as the universe develops. The development of research may shed light on gaps in understanding the process.

For example, why, when these objects merge, nature does not allow their central black holes to easily overcome the "last parsecs" — the final distance of several light years.

— RT-22 in Simeiz is one of the most sensitive radio telescopes in the millimeter range in our country and in the world. It was on it that blazar S 0528+134 was discovered in the 1970s, which even received the personal name Nimfa. It is considered the most powerful emitter in the universe, including in the range of gravitational waves. It is no coincidence that Nimfa has become one of the main objects on the basis of which scientists have built their model," said Yuri Kovalev, Head of the Laboratory of Extragalactic Radio Astronomy at the FIAN Astrocosmic Center.

According to him, this object is being studied on other telescopes around the world. Also, the radiation from S 0528+134 may be available for registration by detectors of the International Pulsar Timing Array, a global project in which astronomers use pulsars (sources of periodic radio signals in space) to determine gravitational waves by distorting the space-time between them and the Earth.