The energetic streams are together 23 million light-years in length—roughly as long as 140 Milky Way galaxies lined end to end

In a distant galaxy, when the universe was just 6.3 billion years old, a feasting black hole gave a long belch. It emitted two gargantuan jets that, according to a new study, are now the largest ever recorded by scientists. Together, the powerful streams stretch 23 million light-years in length—the equivalent of 140 Milky Way galaxies lined end to end.

“You could say this is the largest object that we know of in the universe,” study co-author Martin Hardcastle, an astronomer at the University of Hertfordshire in England, tells New Scientist’s Alex Wilkins.

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Black holes

They are often depicted as rapacious, inescapable gobblers, but occasionally, these messy eaters can spew material, too. As matter falls toward its demise in a black hole, some of that dense detritus heats up, encounters the black hole’s magnetic field and, as a result, escapes its gravitational leash as intense outbursts of light and particles. The light from these emissions can take millennia to reach Earth, so to observe these distant objects is to look back at a time when the outflows cascadedfrom their home base.

The new jet megastructure, described in the journal Nature on Wednesday, is aptly nicknamed Porphyrion, after the giant that warred with the Olympian gods in Greek mythology. Just like the name suggests, every aspect of Porphyrion is immense—its total power output is equivalent to trillions of suns, and its originator black hole probably guzzled a sun’s worth of fuel each year for one billion years straight, Hardcastle tells New Scientist.

“The Milky Way would be a little dot in these two giant eruptions,” study lead author and Caltech astronomer Martijn Oei says in a statement.

Porphyrion’s twin jets came from a supermassive black hole at the heart of a galaxy that’s a dizzying 7.5 billion light-years away from Earth. For one billion years, the gargantuan structure spewed and spewed, its long life enabling the jets to grow to extraordinary lengths.

“I would have thought something like this was impossible,” Laura Olivera-Nieto of Germany’s Max Planck Institute for Nuclear Physics who wasn’t involved in the study, tells New Scientist. “Simply because it seems too big to have maintained the [jet] for so long.”

Unraveling the secrets of this megastructure is no small task. Researchers first discovered Porphyrion using the Low Frequency Array (LOFAR) radio telescope, which uses antennas across Europe. Combing through the LOFAR images required a combination of a discerning eye, machine learning tools and help from citizen scientists. To date, LOFAR has detected more than 10,000 black hole megajets.

To study Porphyrion in further detail, the team roped in a trio of other Earth-based telescopes. The Giant Metrewave Radio Telescope in India and the Dark Energy Spectroscopic Instrument in Arizona allowed the astronomers to find the jets’ birth site: a large galaxy ten times heftier than our Milky Way. Then, the scientists used the W. M. Keck Observatory in Hawai’i to measure the distance between the jets and Earth.

Porphyrion started making its way across the void of space when the universe was just half its present age. During that time, the cosmos was much more congested. Tendrils of the cosmic web—the tangled filaments that form the structure of the universe and contain most of its ordinary matter—huddled closer together. That means the Porphyrion plumes, lengthy even by today’s standards in an ever-expanding universe, outgrew their own galaxy and crossed portions of the web. As such, Porphyrion could have had a literally far-reaching impact on the evolution of the early universe.

The work shows that “jets from black holes can, if circumstances are right, become as large as the universe’s major cosmic structures—galaxy clusters, cosmic filaments, cosmic voids,” Oei tells Reuters’ Will Dunham.

For all their star-chomping notoriety, black holes are also active seeders of new worlds. Outbursts such as Porphyrion could have scattered energy and fodder for stars deep into space. The authors suspect the jet could have also helped spread magnetism across the cosmic void. The extreme length of the twin jets gives scientists much cause to suspect that some black holes’ spheres of influence extend far beyond their home galaxies.

“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,” Oei says in the statement.

Beyond its extreme length and lifespan, the latest jet discovery turns up more surprises about what black holes are capable of. The telescopic observations revealed that Porphyrion’s black hole was in the so-called radiative mode when it belched. In this state, which was common in the early universe, black holes favor releasing energy through fast-moving winds rather than via jet pulses, scientists had thought. Naturally, Porphyrion is a counterexample to that assumption, suggesting to researchers that the universe’s past could contain more extremely long jets emitted by radiative black holes.

“There absolutely could be other jets of equal size or even larger waiting to be found,” Hardcastle tells Robert Lea of Space.com. “We have only surveyed about an eighth of the sky with LOFAR so far. It and other telescopes, such as the forthcoming Square Kilometer Array, will almost certainly find something larger before we are done.”

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