MOSCOW, June 8, Vladislav Strekopytov. Astronomers have discovered thousands of filamentous structures diverging in all directions in the middle of the Milky Way. Their origin is still unclear, but apparently they are somehow connected with the supermassive black hole located there. About how scientists are gradually approaching an understanding of what is happening in the core of our Galaxy — in the material.
«Our» black hole
For a long time, the center of our Galaxy was determined very approximately — somewhere in the constellation Sagittarius — and no specific astronomical object was singled out there. In 1960, a source of radio waves was recorded in this place and named it Sagittarius A (Sgr A). Later it was found that it also emits in the infrared and X-ray ranges.
The movement of stars in the Sgr A region indicates that they are orbiting some invisible compact and very heavy object. This is the black hole Sgr A*. Scientists have calculated that its mass is more than four million times greater than that of the Sun. Similar supermassive black holes are at the center of many other galaxies, and their gravity holds stars and interstellar gas together.
Sgr A* is 27,000 light-years away. A hot, radio-emitting gas cloud is captured in the first image of a black hole, obtained in 2022 using observations from the worldwide network of EHT (Event Horizon Telescope) radio telescopes.
Extremely active place
As technology has advanced, astronomers have learned more and more about the center of our Galaxy. In particular, it turned out that the black hole itself is practically motionless, and the gas cloud surrounding it rotates very quickly, almost at the speed of light. And this causes a constant emission.
In 2010, thanks to one of the world's largest arrays of radio telescopes MeerKAT in South Africa, astronomers discovered huge energy bubbles hundreds of light years in size on both sides of a black hole, emitting in the X-ray and gamma bands. These objects have been explored in detailsaw about a thousand mysterious filamentous structures extending from the galactic center for 150 light-years in the form of thin vertical stripes — filaments. There are single threads and paired threads. They are located approximately at the same distance from each other, like the strings of a harp.
These structures, like bubbles, are observed in a specific range of short waves corresponding to the so-called synchrotron radiation. The electrons, moving at almost the speed of light, collide with magnetic fields, and a distinct radio signal is produced.
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According to the researchers, the filaments are generated by high-energy cosmic ray particles accelerated during a powerful explosion that occurred at the center of the Galaxy several million years ago. Bubbles are also likely associated with this event.
The supermassive black hole at the center of the Milky Way appears relatively calm compared to those in other galaxies. However, the discovered structures indicate that there were periods of activation, when in a short time the black hole absorbed huge masses of dust and gas. This was accompanied by a flash and a release of energy, and the black hole itself acted as a giant particle accelerator.
Scattering in all directions
Recently, the same science team identified signs of yet another type of Sgr A* activity. Having developed a special MeerKAT data processing algorithm, scientists mapped thousands more thread-like structures emanating from the center of the Milky Way.
They all lie in the galactic plane, diverging away from Sgr A*, «like spokes in a wheel.» And much shorter than the vertical ones — from five to ten light years.
“We unexpectedly discovered a new population of structures that point towards the center of the Galaxy,” Professor Yousef-Zadeh said in a press release. “We had to do a lot of work, but we found that these threads are not random and, apparently, are associated with black hole.»
The researchers believe that these filament populations have different origins. Vertical threads are perpendicular to the plane of the Milky Way, they penetrate the Galaxy through and through, and the particles in them move with relativistic speeds. Short horizontal lines are directed radially towards the center and unite thermal particle flows inside the galactic molecular cloud.
Interestingly, their image resembles the dots and dashes of Morse code. In the opinion of the authors, this indicates a discontinuous pulsation of Sgr A* — each segment is formed by a separate emission of high-energy particles. What process inside the black hole controls this pulsation remains a mystery.
“We think that the horizontal filaments originated from some event that happened several million years ago,” says Yousef-Zadeh. “Maybe this is the result of the interaction of material flowing from a black hole with objects located near it.”
The radial filaments discovered by scientists are the smallest of the linear structures of the cosmos. The largest — intergalactic filaments and «great walls» of clusters of galaxies — form a cellular framework of the Universe. They are 50-80 megaparsecs (160-260 million light-years) in size and contain very hot rarefied gas. -type=»photo» data-crop-ratio=»0.728125″ data-crop-width=»600″ data-crop-height=»437″ data-source-sid=»cc_by_20″ class=»lazyload» width=» 1920″ height=»1398″ decoding=»async» />
According to the standard model for the evolution of cosmic matter, intergalactic filaments form along network-like flows of dark matter, which gravitationally attracts ordinary baryonic matter observed astronomers.