Imagine a cosmic structure so large that it would take 140 Milky Way galaxies laid end to end to match it..
Astronomers have just discovered such a phenomenon: the largest black hole jets ever observed, stretching an incredible 23 million light-years across space.
(Credit: E. Wernquist / D. Nelson (IllustrisTNG Collaboration) / M. Oei)
Martijn Oei, a postdoctoral scholar at Caltech and lead author of the underlying paper in Nature, emphasized that our entire galaxy would be just a tiny dot compared to this massive structure.
For those interested, we have written an article that puts these incredible cosmic sizes into a human perspective: How large is the universe? (Universal-Sci) - give it a read if you like.
These types of jets, nicknamed Porphyrion after a giant in Greek mythology, emanate from a supermassive black hole at the centre of a distant galaxy. They shoot out above and below the black hole, releasing energy equivalent to trillions of suns.
Porphyrion dates back to a time when the universe was 6.3 billion years old, less than half its current age of 13.8 billion years.
A Glimpse into the Universe's Distant Past
The discovery of Porphyrion suggests that massive jet systems played a more significant role in the early universe than previously thought.
During that epoch, the cosmic web—a network of wispy filaments connecting galaxies—was more compact. This means that enormous jets like Porphyrion could influence a larger portion of the cosmic web compared to jets observed in the present-day universe.
Gravity shapes the universe by constructing an immense, cobweb-like network of filaments that connect galaxies and galaxy clusters through invisible bridges stretching hundreds of millions of light-years. This structure is called the cosmic web - (Image Credit: Volker Springel (Max Planck Institute for Astrophysics) et al. via ESA)
George Djorgovski, co-author of the study and a professor of astronomy and data science at Caltech explained that astronomers believe that galaxies and their central black holes co-evolve, and one key aspect of this is that jets can spread huge amounts of energy that affect the growth of their host galaxies and other galaxies near them. "This discovery shows that their effects can extend much farther out than we thought."
Unveiling Thousands of Colossal Jet Systems
The Porphyrion jet system is the largest found so far in a sky survey conducted using Europe's LOFAR (LOw-Frequency ARray) radio telescope. This survey has uncovered more than 10,000 faint megastructures, significantly increasing the known population of such giant jets.
Before LOFAR's observations, only a few hundred large jet systems were known, and they were considered rare and generally smaller. According to Martin Hardcastle, second author of the study, Giant jets were known before he and his team started the campaign, but they had no idea that there would turn out to be so many.
The team used a combination of visual inspections, machine-learning tools, and assistance from citizen scientists to identify hes structures. The resulting findings suggest that such massive jets are more common than previously thought.
Smaller' jets are much more common. Seen here are jets emanating from the active black hole in the centre of Centaurus A. - (Credit: ESO/WFI (Optical); MPIfR/ESO/APEX/A.Weiss et al. (Submillimetre); NASA/CXC/CfA/R.Kraft et al. (X-ray) via ESO)
Many questions remain
Despite this discovery, many questions remain. Scientists are still trying to understand how these jets can extend so far without destabilizing and how they influence their surroundings.
The jets spread cosmic rays, heat, heavy atoms, and magnetic fields throughout intergalactic space. Oei: ''The magnetism on our planet allows life to thrive, so we want to understand how it came to be.''
We know that magnetism spreads through the cosmic web, eventually reaching galaxies, stars, and even planets. But the key question remains: Where does it originate? Could these giant jets be responsible for spreading magnetism throughout the universe?
If you are interested in more details about the underlying research, be sure to check out the paper published in Nature, listed below this article.
Sources and further reading on the subject of black holes:
Black hole jets on the scale of the cosmic web (Nature)
Could a human enter a black hole to study it? (Universal-Sci)
A brief history of black holes (Universal-Sci)
What is the size of the universe? (Universal-Sci)
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