A black hole caught feeding on a nearby star kept spitting matter into space even after its outburst nearly faded away.
Astronomers led by the University of Warwick have uncovered new details about how black holes consume and expel matter. Their observations suggest that even faint black holes are not simple bottomless pits. Instead, they may function more like cosmic digestive systems that take in material, process it, and send a large portion back into space.
Black holes are commonly pictured as unstoppable eaters that swallow anything moving too close. However, a detailed study of a dramatic black hole eruption, led by Warwick Postdoctoral Fellow Dr. Noel Castro Segura, reveals a far more complicated process.
A Black Hole Eruption Observed in Detail
Using the European Southern Observatory’s Very Large Telescope (VLT), researchers tracked the newly discovered black hole system Swift J1727.8−1613 during a major eruption in 2023.
The team found that while the black hole pulled gas from a nearby star, it also expelled some of that material through powerful jets and winds. Most importantly, these large outflows continued when the black hole had become extremely faint, and its activity had fallen far below levels previously associated with such behavior.
The findings suggest that black holes do not simply consume everything that approaches them. They may instead process incoming matter and return a substantial amount to space.
“People often imagine black holes simply swallowing everything around them,” said lead author Dr. Noel Castro Segura, a Postdoctoral Fellow at the University of Warwick. “What we’re seeing is a much more complex process. Matter falls in, the system processes it, and a surprising amount is expelled again.”
Watching a Black Hole Change Over Time
The research produced one of the most detailed optical records of a black hole eruption to date. Rather than relying on a small number of isolated observations, astronomers followed the system through several stages of its changing activity.
This allowed them to study the black hole’s feeding behavior as an evolving process instead of viewing it as a single snapshot.
Swift J1727.8−1613 was first detected after it suddenly became active in 2023 and quickly grew into one of the brightest X-ray sources in the sky. The system contains a black hole drawing gas away from a nearby star. As the gas moves inward, it forms a rotating disc of extremely hot material around the black hole.
Because the eruption was observed in real time, astronomers were able to study the feeding process with a level of detail rarely achieved for these events.
Jets, Winds, and a Changing Disc
One of the most notable discoveries involved the relationship between the black hole’s jet and the disc supplying it with matter. As the system launched a powerful jet, researchers also detected major changes within the feeding disc.
These observations provide a rare view of how material moving toward a black hole may be connected to material being thrown back into space.
The biggest surprise appeared after the main feeding frenzy had mostly ended. Even after Swift J1727 had dimmed to roughly one hundredth of its peak activity, the team still found evidence that dense gas was being pushed out of the system.
This means black holes may continue producing strong outflows long after their brightest and most dramatic phase has passed. The total amount of matter expelled could even be comparable to the amount that the black hole ultimately consumes.
Reflecting on the digestive process of black holes, Dr. Noel Castro Segura continued, “If black holes can continue shedding material even after their largest outbursts, it means they may be much less efficient eaters than we previously assumed. A significant fraction of the meal may never reach the black hole at all, changing our understanding of how binary stars in galaxies evolve.”
Black Holes May Be Inefficient Eaters
The observations strengthen growing evidence that black holes are not simply cosmic consumers. They are active systems that both absorb and redistribute matter, drawing material inward while also returning a significant portion to space through jets and winds.
Commenting on the research, Kyle Solomons, Doctoral Researcher at the University of Cape Town, said: “We usually gravitate towards the dramatic fireworks when a black hole outburst begins, but our observations show that the finale can be just as intense. Even as the system’s X-ray emission dropped to a fraction of its peak, it still had enough power to generate a massive expulsion of gas.”
By following Swift J1727.8−1613 throughout a single eruption, astronomers captured nearly the entire cycle of feeding, transformation, and expulsion. The result offers one of the clearest views yet of how black holes react to incoming matter and shape the space around them.
Reference: “Optical outburst evolution of the transient black hole X-ray binary Swift J1727.8−1613: disc response to jet ejections and late-outburst emergence of powerful disc winds” by N Castro Segura, K Solomons, J M Corral-Santana, C Knigge, P A Charles, M Brigitte, S Fijma, M Díaz Trigo, A Gúrpide, D A H Buckley, F Carotenuto, A J Castro-Tirado, D L Coppejans, M Georganti, A Hughes, K S Long, J Matthews, I Monageng, I Pelisoli, T D Russell, D Steeghs, J Svoboda, A J Tetarenko, F M Vincentelli and A G W Wallis, 29 July 2026, Monthly Notices of the Royal Astronomical Society.
DOI: 10.1093/mnras/stag1175
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