Black Holes Don’t Just Swallow, They Digest - UNIVERSE

For decades, black holes have carried a simple reputation: cosmic vacuum cleaners that pull in everything nearby and never let go. New observations suggest that picture is incomplete, and a little too tidy.

Astronomers led by Dr. Noel Castro Segura at the University of Warwick tracked a stellar-mass black hole system called Swift J1727.8−1613 through a dramatic outburst that began in 2023. Using the European Southern Observatory’s Very Large Telescope, the team watched as the black hole pulled gas from a nearby companion star, the classic feeding behavior everyone expects. But it also expelled large amounts of that material back out through powerful jets and winds, and kept doing so even after the outburst had visibly faded.

That’s the surprising part. Black hole activity is usually judged by brightness, how much light the infalling matter gives off as it heats up. This system kept expelling gas at roughly the same rate it was consuming material even after it had dimmed to about one-hundredth of its peak brightness. In other words, the black hole looked like it had gone quiet, but it was still actively processing and returning matter to its surroundings.

The findings help settle a longer-running debate in astrophysics about whether black holes eject material through jets (narrow, fast-moving beams) or winds (broader, slower outflows), or both at once, and under what conditions. Earlier work on a different system had suggested jets and winds were mutually exclusive, only one active at a time. The Warwick team’s data on J1727 offers a rare direct measurement showing outflow can roughly match inflow even at low accretion rates, a number theorists need to refine their models of how black holes shape the galaxies around them.

It’s a small but telling correction to a story we thought we already understood: black holes aren’t just consuming machines. They’re closer to a digestive system, taking in, processing, and returning a surprising share of what they catch.

Source: University of Warwick / ESO, published July 31, 2026, in Monthly Notices of the Royal Astronomical Society.

Original paper: 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 (arXiv preprint, MNRAS). 

Source: Black Holes Don’t Just Swallow, They Digest