Astronomers studying the 2023 eruption of binary black hole system Swift J1727.8−1613 discovered that it discharged massive amounts of matter into space instead of swallowing everything, revealing that black holes act more like digestion systems than bottomless pits.
Observing a Black Hole Feed and Expel Matter
Black holes are some of the most awe-inspiring and mysterious celestial objects in the universe. This is primarily because astronomers still don’t understand the underlying mechanisms that drive black holes, including its formation, evolution, and end. As their name implies, black holes can’t be viewed directly since they blend into the background of the vastness of space. Therefore, astronomers are limited to “seeing” black holes when they consume other celestial objects, most notably stars. When this happens, the astronomers see the light from the star being violently consumed by a nearby black hole in a spectacular display. However, astronomers are still puzzled regarding what happens after the consumption. Now, an international team of scientists led by the University of Warwick might be one step closer to solving this galactic conundrum regarding how a black hole consumes objects. In findings recently published in the Monthly Notices of the Royal Astronomical Society, the researchers present new evidence regarding the binary black hole system, Swift J1727.8−1613, discussing how some materials consumed by Swift J1727.8−1613 are discharged back out where it came from.
The reason Swift J1727.8−1613 is a binary black hole system is because it consists of a large black hole with a normal-sized star orbiting it. In this case, the black hole is estimated to be approximately 10 times the mass of our Sun with the black hole consuming pieces of its companion star. This exciting discovery was made using the European Southern Observatory’s Very Large Telescope (VLT), which observed a 2023 eruption from Swift J1727.8−1613 that displayed material being discharged as winds and jets violently being expelled from the black hole. While black holes are typically observed through single images, the astronomers used the VLT to make several observations over time, enabling them to watch the sequence of events from consumption to eruption.
Cosmic Indigestion and Inefficient Eating Habits
The team notes that Swift J1727.8−1613 is a small and less active black hole than how others have been observed, suggesting black holes act function more on digestion instead of being endless pits where nothing escapes. Essentially, Swift J1727.8−1613’s small size might have been too full to fit all the material and “barfed” up the leftovers, with these eruptions lasting for extended periods of time. A key finding was that even after the black hole was done with its “meal”, the eruption continued. 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. 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.
Data gathered from the Very Large Telescope challenged long-held assumptions about how these dense objects operate. Rather than acting as endless pits where matter disappears permanently, the system displayed behavior akin to a bad case of cosmic indigestion. 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,
said Dr. Noel Castro Segura, who is a Postdoctoral Fellow at the University of Warwick.
Castro Segura noted that the observations point to a much more complex process where matter falls in, the system processes it, and a surprising amount is expelled again. The research team discovered that the most massive outflows occurred when the feeding activity was much lower than previously expected.
“What we’re seeing is a much more complex process. Matter falls in, the system processes it, and a surprising amount is expelled again.”
Noel Castro Segura, University of Warwick
Connecting Accretion Disks and Fuel Cycles
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 ti…
