Astronomers have spotted the biggest pair of black hole jets ever seen, spanning 23 million light-years in total length. That's equivalent to lining up 140 Milky Way galaxies back to back.
"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," says Martijn Oei, a Caltech postdoctoral scholar and lead author of a new Nature paper reporting the findings. "The Milky Way would be a little dot in these two giant eruptions."
The jet megastructure, nicknamed Porphyrion after a giant in Greek mythology, dates to a time when our universe was 6.3 billion years old, or less than half its present age of 13.8 billion years. These fierce outflows-with a total power output equivalent to trillions of suns-shoot out from above and below a supermassive black hole at the heart of a remote galaxy.
Prior to Porphyrion's discovery, the largest confirmed jet system was Alcyoneus, also named after a giant in Greek mythology. Alcyoneus, which was discovered in 2022 by the same team that found Porphyrion, spans the equivalent of around 100 Milky Ways. For comparison, the well-known Centaurus A major jet system, the closest such system to Earth, spans 10 Milky Ways.
The latest finding suggests that these giant jet systems may have had a larger influence on the formation of galaxies in the young universe than previously believed. Porphyrion existed during an early epoch when the wispy filaments that connect and feed galaxies, known as the cosmic web, were closer together than they are now. That means enormous jets like Porphyrion reached across a greater portion of the cosmic web compared to jets in the local universe.
"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," says co-author George Djorgovski, professor of astronomy and data science at Caltech. "This discovery shows that their effects can extend much farther out than we thought."
