“The dimensions are enormous,” says Gabriela Calistro Rivera, a 34-year-old Peruvian astronomer who currently works for the German Space Agency. Together with colleagues from Europe and the United States, Calistro announced today the discovery of the largest jets ever observed in the universe. They are produced by Porphyrion, a previously unknown supermassive black hole that spits out two jets in opposite directions, and which together span 23 million light years. It is a previously unthinkable distance that would be equivalent to lining up 140 galaxies like the Milky Way, one after the other.
Porphyrion is named after the largest of the giants in Greek mythology. It is a supermassive black hole of the type that exists at the center of all galaxies, including our own. It appeared about 6.3 billion years ago, when the universe was barely half its current age. The energy contained in the two jets of Porphyrion is equivalent to that produced by billions of stars like the Sun, or by the collision of two galaxy clusters. The discovery — a “record,” as Calistro points out — is published this Wednesday in Naturea benchmark for the best science in the world.
Porphyrion’s emanations are called relativistic jets, because the particles they contain – electrons, protons, heavy atoms – are close to the speed of light, the maximum speed limit in the universe, according to the theory of relativity, formulated by Albert Einstein more than a century ago. The laws of physics determine that nothing can escape a black hole. What falls into it never comes out. Relativistic jets are produced just before that moment by the enormous friction of all the matter that rotates around it. Part of it is propelled with enormous energy in two narrow beams. It is the most powerful radiation in the universe.
The team used LOFAR, a low-frequency radio telescope based in the Netherlands, but with huge antennas spread across several European countries. The observatory picks up low-frequency radio waves, the kind of signals that can reach Porphyrion given its remoteness and age. Until now, it was thought that there were relatively few black holes with large jets: only a few hundred had been observed. But thanks to the European telescope, the team has now found 11,000.
The largest jet system confirmed so far was Alcyoneus, also named after a giant from Greek mythology, which was discovered in 2022 by this same team, and which spans about 100 Milky Ways. By comparison, the jets of Centaurus A, the closest system to Earth, are ten times smaller.
Porphyrion is a giant only in appearance. Within its galaxy, it is basically like a coin that is at the center of the Earth, explains Calistro. “It is incredible that this tiny black hole, even though it is very massive, can have an influence on this entire galaxy.” But “the craziest thing,” she warns, is that Porphyrion’s jets reach hundreds of times farther, and influence the composition of the universe on the largest known scales. Theoretical models that try to explain the physics of these jets never predicted such enormous beams, the astronomer admits: “It is something that has never been seen before.”
The discovery forces us to rethink the role of black holes in the evolution of the universe. They are no longer just fearsome monsters of destruction, but gardeners that dominate the growth and evolution of the galaxies that grow around them. Currently, the details of how this phenomenon occurs are one of the most active fields of research. One of the possible explanations is that relativistic jets increase the temperature of the galactic environment, which prevents the gas from collapsing to form new stars, Calistro explains.
The supermassive black hole at the centre of the Milky Way, Sagittarius A*, is dormant. But it may have once spewed out powerful relativistic jets, as suggested by two enormous bubbles observed above and below the galaxy, so large that it would take 50,000 years to travel across them at the speed of light.
Astronomers have also used other telescopes in India and the United States to determine that the galaxy in which Porphyrion resides is about 10 times more massive than the Milky Way. Due to the constant expansion of the universe, which is one of the most unknown phenomena in the cosmos, it is now 7.5 billion light years away.
The LOFAR telescope has covered only 15% of the entire sky, so it has possibly only discovered “the tip of the iceberg,” he explains in a note Martjin Oeian astronomer at the California Institute of Technology (United States) and first author of the study.
There may be many other similar objects that emerged in the early stages of the universe, which contradicts current theories. “Until now, these giant jet systems seemed to be a phenomenon of the recent universe. If distant jets like these can reach the scale of the cosmic web, then it is possible that all regions of the universe have been affected by black hole activity at some point in cosmic time,” Oei explains.
The researcher wants to continue investigating the effect of these megastructures at a cosmological level, especially that of magnetic fields. “On our planet, magnetism allows life to thrive, so we want to understand how it arose,” he says. “We know that magnetism permeates the cosmic web, then reaches galaxies and stars, and eventually planets, but the question is: where does it start? Have these gigantic jets dispersed magnetism throughout the cosmos?”
Antxón Alberdi, director of the Institute of Astrophysics of Andalusia, who did not participate in the study, highlights its importance, as it details how black holes can influence the evolution of the cosmos on time and space scales that current models do not reproduce well. It is thought that in its origin the universe was formed by filaments that connected the different galaxies. With time and the expansion of the cosmos, these filaments moved away, forming a huge scaffolding known as a cosmic web. The work shows that Porphyrion and its galaxy “appeared not in an empty space, as is usual, but in one of the filaments, which implies that their magnetic fields and particles may have connected galaxies to each other” and influenced their evolution, he points out.
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