Stellar Orbits Reveal the Secrets of Eruptions Near Black Holes

The study, published in the prestigious journal Astronomy & Astrophysics, focused on so-called quasiperiodic eruptions—repeating flares that can recur on timescales of hours to days. These phenomena allow scientists to probe otherwise difficult-to-observe, quiescent galactic nuclei. At the centers of most galaxies reside supermassive black holes, whose masses can be millions to billions of times that of the Sun. If they are not actively accreting surrounding material, they are almost “invisible.” The eruptions act as natural beacons that draw attention to these objects. “It is truly unusual and at the same time very puzzling to observe regular flashes from the depths of the cosmos, especially from the immediate vicinity of supermassive black holes,” says Martin Mondek, a master student of astrophysics at Masaryk University, clearly excited and enthusiastic about the phenomenon.

According to scientists, these flares most likely arise when a star passes through a dense disk of gas surrounding the black hole. “During the collision, the disk material is heated to extreme temperatures and begins to radiate intensely,” Mondek adds. The new research also explains why these eruptions gradually weaken. A key role is played by the accretion disk that formed after the destruction of another unfortunate star, which ventured too close to the black hole and was completely torn apart. “The remnants of this star formed a disk in the immediate vicinity of the supermassive black hole, through which a second, surviving star periodically passes. The disk gradually thins due to mass loss and viscous spreading - and along with it, the observed flares fade,” explains Michal Zajaček, co-author of the study and supervisor of Martin Mondek.

The research involved a team of experts from several Czech academic institutions. The principal investigator was Martin Mondek from Masaryk University, who collaborated on the project with his supervisor Michal Zajaček, who is also based at the same department. The team also included Henry Best and Petr Kurfürst from the same university, Taj Jankovič from the Institute of Physics of the Czech Academy of Sciences, and Vladimír Karas from the Astronomical Institute of the Czech Academy of Sciences. The results of the study show that students can be fully-fledged contributors to cutting-edge scientific research and participate in projects with international reach, including publications in prestigious academic journals.

The research was partially supported by a Czech Science Foundation Junior Star grant titled “Stars in Galactic Nuclei: Their Interaction with Massive Black Holes,” whose principal investigator is Michal Zajaček.

DOI: https://doi.org/10.1051/0004-6361/202558531