At the center of our Galaxy, roughly 26,000 light-years from Earth, sits the supermassive black hole Sagittarius A* (Sgr A*). For billions of years, it has remained relatively "dormant," occasionally consuming small portions of gas. Theory has long predicted that when feeding this way, a black hole should not only swallow material but also expel some of it back as powerful winds. However, direct evidence of this phenomenon from our own black hole had long been elusive. Now, through observations from the ALMA radio telescope and the Chandra X-ray Observatory, scientists have finally witnessed this "breath."
Researchers Mark Gorski and Lena Murchikova spent several years gathering ALMA data at a wavelength of 1.3 millimeters. They focused on the emission of carbon monoxide (CO) molecules—a reliable indicator of cold molecular gas in the black hole's vicinity, just a few light-years (about one parsec) away. The task was daunting: Sgr A* itself shines brightly in the radio spectrum, and its rapidly fluctuating emissions drown out the faint signals from the surrounding gas. To overcome this, the scientists had to develop sophisticated methods for modeling and subtracting this background noise.
The results exceeded expectations. The new map proved to be roughly 100 times more sensitive and 80 times higher in resolution than previous attempts. It clearly revealed a massive, cone-shaped cavity in the cold gas—a vast "void" pointing directly away from the black hole. Precisely where the cold gas vanished, Chandra data showed the area filled with hot, X-ray-emitting gas. This is the classic signature of an active wind: a hot stream erupting from the black hole's surroundings, either sweeping away cold material or heating it until it becomes invisible at radio wavelengths.
According to the authors' estimates, this wind has been blowing for at least 20,000 years. While relatively weak compared to the powerful jets found in active galaxies, it is a significant phenomenon for our own quiet Galactic center. It helps explain how a supermassive black hole regulates its intake of gas and influences the evolution of its surroundings—from star formation to the dynamics of the central regions.
This discovery is the culmination of years of meticulous work and innovative data processing. It resolves a half-century-old mystery and provides astronomers with a new tool for understanding the behavior of "dormant" black holes. We are now one step closer to visualizing what occurs at the very heart of the Milky Way, where the giant’s quiet "breath" shapes the surrounding cosmos.
The discovery was published in The Astrophysical Journal Letters (arXiv:2509.10615).
