Astronomers led by the University of Warwick have uncovered what they describe as a kind of cosmic digestive system around a black hole: even when a black hole appears faint, it may still be actively expelling large amounts of matter rather than simply swallowing everything nearby.
Using the European Southern Observatory's Very Large Telescope (VLT), the team tracked the recently discovered black hole system Swift J1727.8−1613 throughout a spectacular eruption in 2023, when it became one of the brightest X-ray sources in the sky. As the black hole pulled gas from a nearby companion star, forming a rapidly spinning disc of superheated material, it also sent material back into space through powerful jets and winds — and these large outflows continued even when the black hole dimmed to roughly one hundredth of its peak activity.
'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.' The research produced one of the most detailed optical records ever assembled of a black hole outburst, allowing astronomers to watch nearly the full cycle of feeding, transformation and expulsion in real time — including a striking moment when the black hole launched a powerful jet as its feeding disc underwent major changes.
'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,' said Kyle Solomons, a doctoral researcher at the University of Cape Town. '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.' The findings, published in the journal Nature Astronomy on July 28, suggest the amount of material a black hole ejects over time could be comparable to what it eventually consumes — meaning black holes may be much less efficient eaters than previously assumed, with implications for how binary stars in galaxies evolve and how matter is redistributed across the universe.
