A black hole mystery has been solved after half a century, according to Northwestern University researchers who discovered evidence of a long-missing cosmic wind emanating from the center of the Milky Way.
Sagittarius A* (Sgr A*) is the supermassive black hole that acts as a central anchor to the Milky Way galaxy, and should produce a wind or jets as back flow when it consumes matter. However, no one had ever managed to capture evidence of this theoretical black hole wind blowing through the Milky Way.
That is, until now, as detailed in a recent study published in The Astrophysical Journal.
Black Hole Wind
“Unless a black hole exists in a perfect vacuum, it must blow a wind somehow,” said co-author Mark Gorski, a Fellow in the Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) at Northwestern University.
“And there is no perfect vacuum in the universe,” Gorski added. “With new observations, this is the first time we’ve had a clean enough view to see the wind’s imprint. We looked at the data and said, ‘There it is. There is the thing that everybody’s been looking for for 50 years.’”
Although black holes are popularly conceived of as a one-way path, this isn’t entirely true. Infalling material picks up speed on its journey, eventually approaching the speed of light and producing such quantities of energy that a backflow is created, pushing material back out as jets or wind.
The lack of any outflow observations of Sgr A* has created confusion among astronomers, as the absence of such activity would make the Milky Way’s central black hole an extreme outlier. As a solution to this mystery, the Northwestern team says that Sgr A* is likely in a quiet phase, which makes these outflows subtle and difficult to detect.
“We were the first to show that molecular gas very, very close to the black hole is feeding it,” said co-author Elena Murchikova. “The wind is not powerful, and its direction probably wanders with time. It shows that our black hole is not unique, and our place in the universe is not unique.”
Peering into the Galactic Center
“To observe our own black hole, we have to look through the plane of our galaxy,” Murchikova said. “That means we have to peer through gas, dust, and ionized structures, and you can’t really see through all of that easily.”
Chile’s Atacama Large Millimeter/Submillimeter Array (ALMA) radio telescopes provided the researchers with a five-year catalog of deep observations, from which they constructed the highest-resolution image of cold molecular gas around a black hole ever assembled.
The gas in the image is less than three light-years from the black hole, relatively close on the scale of a 100,000- to 120,000-light-year-wide galaxy. After the researchers refined the data to remove the black hole’s radio signals, the image had 80 times the clarity and 100 times the depth of any previous map of the Sgr A* region, allowing the team to resolve previously hidden structures.
The most notable of these revelations is the cone-shaped cavity about 45 degrees wide and three light-years long, devoid of molecular gas. The team says that only the wind from Sgr A* blowing away or heating cold gas could account for this strange empty pocket in space.
Solving the Black Hole Mystery
“If you blow hot material from the black hole, it’s not going to want to exist with the cold material,” Gorski said. “It’s either going to push the cold material out or heat it up. And, if it’s too hot, you will no longer see the cold gas.”
The team says the size of the empty region is too large to have been created by stellar winds, even if all the nearby stars were acting in concert. To confirm their findings, the team looked to data from NASA’s Chandra X-ray Observatory, which showed bright X-ray emission from the cone region.
“When you find something that no one has seen before, the first thought that runs through your mind is not ‘Oh my god, we made a discovery,’” Murchikova said. “It’s ‘Oh my god, what’s wrong with my analysis?’ But when we overlaid our image with the X-ray image, it started to make sense.”
From the length of the cone, the researchers estimate the black hole wind has been pushing into the ionized gas for at least 20,000 years to penetrate so deeply. The finding confirms that Sir A*’s behavior may be quiet compared to the supermassive black holes observed at the cores of other galaxies, but it is still active to a small degree.
“The majority of other galaxies spend most of their lives in a state where they are not particularly active,” Murchikova concluded. “But we can only see them when they are in a fireworks stage. It is very attractive to study black holes when they are in the fireworks stage, but that’s not actually their dominant state. Sgr A* finally gives us a window into the life of a black hole in this quiet state.”
The team’s paper, “The Discovery of a Large Active Wind from the Milky Way’s Central Black Hole,” appeared in The Astrophysical Journal on June 4, 2026.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.