Biggest pair of black hole jets ever seen

Astronomers have discovered the largest pair of black hole jets, stretching 23 million light-years. That’s like lining up 140 Milky Way galaxies one after another! These huge jets, named Porphyrion after a giant from Greek mythology, are believed to have originated when the universe was 6.3 billion years old, less than half its current age of 13.

8 billion years. The jets shoot out from above and below a supermassive black hole in a distant galaxy and are as powerful as trillions of suns. Before Porphyrion, the largest confirmed jet system was Alcyoneus, also named after a giant, which was found in 2022.



Alcyoneus is about 100 Milky Ways long. The closest major jet system, Centaurus A, is only 10 Milky Ways long. This new finding suggests that giant jets like Porphyrion may have played a bigger role in forming galaxies in the young universe than we thought.

Porphyrion existed when the cosmic web, the structure connecting galaxies, was closer together, allowing these massive jets to reach further than jets do today. Martijn Oei, a Caltech postdoctoral scholar and lead author of a new Nature paper reporting the findings, said, “This pair is not just the size of a solar system or a Milky Way; we are talking about 140 Milky Way diameters in total. The Milky Way would be a little dot in these two giant eruptions.

” Co-author George Djorgovski, professor of astronomy and data science at Caltech, said, “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.” The Porphyrion jet system is the largest discovered in a sky survey that found over 10,000 similar faint megastructures.

This huge jets were detected using Europe’s LOFAR (LOw-Frequency Array) radio telescope. Martin Hardcastle, second author of the study and a professor of astrophysics at the University of Hertfordshire in England, said, “Giant jets were known before we started the campaign, but we had no idea that there would turn out to be so many. Usually, when we get a new observational capability, such as LOFAR’s combination of wide field of view and very high sensitivity to extended structures, we find something new, but it was still very exciting to see so many of these objects emerging.

” In 2018, Oei and his team started using LOFAR to study the cosmic web, the thin filaments connecting galaxies. While looking at radio images of these filaments, they unexpectedly discovered several very long jet systems. “When we first found the giant jets, we were surprised.

We had no idea there were so many,” Oei said. The team carefully examined the radio images to find more hidden jets, used machine-learning tools to spot potential jets, and invited citizen scientists worldwide to help look through the images. The team used the Giant Metrewave Radio Telescope (GMRT) to determine the exact location of the galaxy from which Porphyrion originated.

They also used ancillary data from a Dark Energy Spectroscopic Instrument (DESI) project. Using the W. M.

Keck Observatory in Hawai‘i, scientists confirmed that Porphyrion is 7.5 billion light-years from Earth. “Until now, these giant jet systems appeared to be a phenomenon of the recent universe,” Oei says.

“If distant jets like these can reach the scale of the cosmic web, then every place in the universe may have been affected by black hole activity at some point in cosmic time.” Observations from the Keck telescope showed that Porphyrion comes from a radiative-mode active black hole, not one in a jet-mode state. When supermassive black holes become active, their strong gravity pulls in and heats surrounding material.

They can then release energy either as radiation or as jets. It was surprising because astronomers did not know this mode could produce such huge and powerful jets. What’s more, it lies in the distant universe where radiative-mode black holes abound, the finding implies there may be a lot more colossal jets left to be found.

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