Astronomers discover that quasars are not nailed to heaven

Until recently, it was thought that quasars had essentially fixed positions in the sky. While near-Earth objects move on complex trajectories, the quasars are so far apart that it was thought that they provided stable and reliable reference points for navigation and plate tectonics research. An international team of astrophysicists, made up of researchers from the Moscow Institute of Physics and Technology, discovered that the quasars were not totally immobile and explained this behavior. The results were published in the Monthly Notices from the Royal Astronomical Society.

"The apparent positions of the quasars change with the radiation frequency used to observe them.The researchers predicted this effect about 40 years ago on the basis of synchrotron radiation theory and observed it shortly thereafter" , says Alexander Pushkarev, leading researcher at the Crimean Astrophysical Observatory and Lebedev Physical Institute of the Russian Academy of Sciences. "Our study aimed to determine whether this effect varies over time and, if so, on what time scales and to what extent the change in apparent position changes."

Quasars belong to a larger class of astronomical objects called active galactic nuclei. Fortunately, none of them is located near the Earth. An AGN is basically a "fire-breathing" black hole incinerating its environment with two opposing plasma streams moving at relativistic speeds. Covered in the heart of an AGN, the black hole itself is naturally invisible. This central object is surrounded by a region that can only be penetrated by the highest frequency radiations. As a result, an Earth-based observer sees an AGN differently depending on the radiation frequency used. For example, while optical observations reveal the jet and the glow around its source, radio telescopes can discern only the part of the Quasar "tail" directed at us.

The most accurate technique currently available for radio observation of distant objects is known as very long-base interferometry. It is based on a giant imitated telescope that relies on many regular instruments scattered around the world. Such a "virtual" telescope can obtain high resolution data on a remote radio source. However, reducing data and restoring a "picture" of the target is not an easy task, as researchers need to recover an image from information collected by many instruments.

The team has developed an automated procedure to solve this task. They found that the apparent apex coordinate of the jet does not remain static, but fluctuates in both directions along the jet axis. It seems that the source itself is "wiggling". However, astrophysicists consider these fluctuations as a kind of illusion. They explain the phenomenon in terms of the complex nature of radiation. This implies that the quasar nuclei themselves do not undergo any movement in space.

"In the twentieth century, a theory explained the apparent behavior of quasars in terms of fast electron radiation, but this model does not explain how this radiation can vary," said Alexander Plavin, a researcher at the Laboratory for Basic Research and Research. applied MIPT. of relativistic objects of the universe and doctoral student at the Institute of Physics of Lebedev, RAS. "Until recently, it was more convenient to simply ignore this variability – it was assumed that AGNs were statistically static for practical reasons, but we have accumulated enough data and developed an efficient and accurate method for automated processing. allowed us to detect the variability of position and interpret it in terms of the internal physics of the jets ".

What could be the reason behind this phenomenon? To answer this question, the authors verified the potential correlations with some of the variable quasar parameters, such as their brightness or magnetic fields, in apparent AGN positions. It has turned out that the apparent coordinates of an active galactic core are directly associated with the particle density in the jet: the higher the brightness, the higher the perceived positional shift. This could complement the quasar theoretical models by indicating the role of nuclear explosions injecting higher density plasma into the outgoing flux.

This analysis also has a practical dimension. New, accurate data on apparent offsets of quasar positions will correct astrometry techniques, leading to the most accurate navigation systems in the history of mankind.