Astronomers have used the Very Large Telescope (VLT) to observe the violent outflow of material from a distant black hole. The observation once again shows that even the hungriest black holes are extremely messy eaters, while also revealing the “digestive processes” of these cosmic titans in unprecedented detail.
The research focuses on the black hole system Swift J1727.8−1613, located around 8,800 light-years away, and a violent bout of cosmic indigestion and the bright eruptions the system triggered back in 2023. That episode is what initially led to the discovery of Swift J1727.8−1613 in 2023, and it resulted in the system becoming one of the brightest X-ray sources in the sky over Earth.
A team of astronomers has now discovered that as this black hole greedily stripped a star of its stellar material, some of this matter was consumed, but other stellar material was blasted back into space as high-speed jets and powerful black hole winds. They also found that the most massive outflows of material happened when the black hole’s feeding activity was much lower than previously thought. The upshot of this is the conclusion that black holes aren’t quite the “bottomless pits” scientists had assumed, but are far more like complex cosmic digestive systems.
“People often imagine black holes simply swallowing everything around them,” team leader Noel Castro Segura of the University of Warwick in the UK said in a statement. “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 changing face of a feeding black hole
Swift J1727.8−1613 consists of a black hole surrounded by a swirling platter of material pulled away from a companion star. This matter still has angular momentum, or rotation, so it can’t directly fall to the black hole, but instead forms this structure, called an accretion disk.
The immense gravitational influence of the black hole generates intense tidal forces and friction in the accretion disk, superheating it and causing it to glow brightly.
The observations of this glowing disk conducted by Segura and colleagues differ from previous studies of black hole outbursts because their detailed study allowed them to watch the Swift J1727.8−1613 system change over time as it fed on a star.
The resulting “movie” of this feeding black hole revealed that as the cosmic titan blasted out jets, the accretion disk slowly feeding it underwent changes of its own.
That gives scientists a rare and fleeting insight into the connection that exists between matter falling to the maw of a black hole and the material being blasted out at near light-speed as jets of plasma.
The team also found that even after the feeding frenzy of this black hole had subsided, it seemed to still be powering black hole winds of dense gas. They suggest that the amount of material flung away by the black hole may eventually amount to the same mass as that consumed by the black hole, meaning half of its stellar meal was eventually lost to space.
“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,” Segura added. “A significant fraction of the meal may never reach the black hole at all, changing our understanding of how binary stars in galaxies evolve.”
The fact that this team was able to observe the entire feeding cycle of this black hole from its initial flare to its dramatic and rather windy end paints a clearer and more dynamic picture of this process than scientists have ever had access to before.
“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,” Kyle Solomons, Doctoral Researcher at the University of Cape Town, said.
The team’s research was published on Wednesday (July 29) in the Monthly Notices of the Royal Astronomical Society (MNRAS).