Symposium “Traversing the Galactic Center in Space and Time” in Nature Lead

From the black hole to the birth of new stars 

At the very heart of the Milky Way lies the supermassive black hole Sagittarius A* (Sgr A*), with a mass of approximately four million Suns. But the Galactic Center is much more than just a black hole. It is surrounded by millions of stars and vast regions of gas and dust from which new stars can form. 

One of the main messages of the Brno symposium was that all these components should be viewed as a single interconnected and constantly evolving ecosystem. Gas flows toward the center of the Galaxy, new stars form from it, and some of the material eventually reaches the black hole. At the same time, both stars and the black hole can influence their surroundings through winds, explosions, and outflows of matter. 

Although the center of the Milky Way contains an enormous amount of gas, Sgr A* is surprisingly inactive today. Only a tiny fraction of the available material reaches its immediate vicinity. The center of our Galaxy therefore serves as a natural laboratory in which we can observe how a massive black hole, stars, and interstellar matter interact with one another. 

A sleeping giant at the center of the Milky Way 

The black hole’s current quiet state, however, should not be taken for granted. Observations show that Sgr A* was much more active in the past. X-ray “echoes” in surrounding gas clouds provide evidence of significant activity several centuries ago, while enormous structures extending above and below the plane of the Galaxy point to even stronger activity several million years ago. 

The Galactic Center is therefore far from an unchanging environment. It probably undergoes repeated cycles of quieter and more active periods, during which the black hole, stars, and surrounding gas evolve together. 

Brno as a center of international astronomy 

IAU Symposium 405 was the fifteenth meeting in a long-running international series of workshops devoted to research on the Galactic Center, which began at Caltech in Pasadena, California, in 1982. This was the first time the community gathered in Brno. 

The symposium also highlighted Brno’s scientific heritage. Alongside Gregor Johann Mendel, the program featured two Brno-born scholars, Ernst Mach and Kurt Gödel, whose work has surprising connections to modern astrophysics. 

Despite the tremendous progress made in recent years, many questions remain unanswered. Astronomers are still investigating, for example, how young stars could have formed so close to the black hole, how often Sgr A* awakens into periods of stronger activity, and how many other, smaller black holes may be hidden in the center of the Galaxy. 

New observatories such as the Extremely Large Telescope and the Square Kilometre Array Observatory, together with further observations by the James Webb Space Telescope, will help astronomers address these mysteries. The Brno symposium demonstrated that the center of our own Galaxy remains one of the best laboratories for understanding what happens in the nuclei of galaxies throughout the Universe. 

References: 

Michal Zajaček , Bożena Czerny, Martin Mondek, Samik Mitra, Matúš Labaj, Tomáš Ondro , Jan Janı́k , Jiřı́ Dušek: IAU Symposium 405: Traversing the Galactic Center in Space and Time, Nature Astronomy 

https://www.nature.com/articles/s41550-026-02958-8 

doi:  10.1038/s41550-026-02958-8