2023 Author: Bryan Walter | [email protected]. Last modified: 2023-05-21 22:24
Analyzing observations in the X-ray range, astrophysicists discovered structures about a hundred parsecs in size in the center of our galaxy, which they called "chimneys." The authors believe that along these formations, matter and energy from processes in the very center of the Milky Way move to Fermi bubbles - giant regions outside the galactic plane filled with hot gas. The results are published in the journal Nature.
At the center of the Milky Way is a supermassive black hole. If a significant amount of matter falls on such an object, then it is active: gravitational energy is converted into thermal energy, an intense glow appears, and part of the falling matter is thrown back in the form of jets. In particular, such processes should be responsible for the observed properties of quasars.
The black hole in the Milky Way, also called Sagittarius A *, is not very active at the moment. However, there are indications that it was noticeably more active millions of years ago. One of these facts is the existence of Fermi bubbles - two regions filled with very hot gas, over seven kiloparsecs in size, located outside the plane of the galaxy right at its center. According to one of the existing hypotheses, they appeared due to jets of high-energy particles from the center of the Milky Way, which beat at the time of a high rate of absorption of matter by a black hole. According to an alternative view, they are associated with an active stage of star formation, when many large and hot stars with strong winds appeared, which ended up relatively quickly in the form of supernovae. Today, these bubbles are observed as two huge spots in the gamma range, and their boundaries near the galactic plane are also visible in the X-ray range.
Another evidence of the activity of Sagittarius A * is the structures of about 15 parsecs, observed both in the radio and in the X-ray range. They are in close proximity to the central object and indicate the existence of collimated flows of matter from it. However, on an intermediate scale, only one 150 parsec asymmetric radio emission region was known. The work, led by Gabriele Ponti of the Max Planck Institute for Extraterrestrial Physics, describes the discovery of two regions of intermediate size in the X-ray range. They stretch from the center of the Milky Way to the base of the Fermi bubbles. Astrophysicists have called them "chimneys" through which matter moves, either from supernova explosions or ejected by a black hole.
X-ray structure of the center of the Milky Way. In the center of the image there is a black hole, asymmetric ovals are galactic chimneys, white arcs are the borders of Fermi bubbles, the plane of the Galaxy is marked with a horizontal line.
“We know that the flows of matter and energy emanating from the galaxy play a defining role in the formation and change of its appearance - they are a key component that affects how galaxies and other structures form and evolve,” says Ponti. "Fortunately, our Galaxy provides us with a close laboratory for detailed research and study of the movement of streams in space around us."
The authors write that the "chimneys" are traced to the galactic latitude of about 0.2 degrees and are structurally associated with a region with a radius of 15 parsecs adjacent to the black hole. In this central region, a very strong dependence of the surface brightness in the X-ray range on distance is observed, which indicates the presence of a significant pressure gradient that cannot be compensated by gravity. Therefore, here matter must move from the central area.
Scientists' estimates show that the thermal energy contained in the region immediately adjacent to the center and in the "chimneys" may well be explained by both supernova explosions in the central cluster and the activity of a black hole, for example, the tidal destruction of a star that has flown too close to occur every few thousand years. … Therefore, the authors still find it difficult to say exactly which process is responsible for the appearance of these structures.
The most central region of the Milky Way is of significant interest for science, therefore, many works are devoted to its study. In particular, scientists have found that this area began to form 11 billion years ago, the black hole located there helps the formation of stars, and objects that are not found in other places are also observed there.
