Longest, Strongest Black Hole Jets Ever Observed, Spanning 24m Light-years

Porphyrion’s Record-Breaking Black Hole Jets Stretch 24 Million Light-Years, Shaping the Universe’s Largest Structure

TL;DR

Porphyrion, a galaxy with supermassive black hole jets, has shattered records with jets extending 24 million light-years—outpacing Alcyoneus by 8 million light-years. This vast structure challenges previous beliefs about how large cosmic jets can become. These jets, spanning two-thirds of a cosmic void, demonstrate black holes’ unexpected ability to shape the universe. The jets have stayed coherent for billions of years, highlighting the role supermassive black holes play in cosmic evolution, suggesting they could be responsible for magnetizing intergalactic space and influencing large-scale structures across the universe.

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How much impact can a single object in the universe have? Until recently, we didn’t think it was much. Sure, individual objects can emit various things: photons of different wavelengths, neutrinos, powerful gravitational waves, and jets of energetic particles that span across thousands, even millions of light-years. For instance, massive collapsing stars can create supernovae, neutron stars merging can lead to kilonovae, and supermassive black holes can form active galactic nuclei or quasars. Under the right circumstances, these objects can outshine the combined energy of all stars in their galaxies.

However, this won’t last. Unlike the stable light from stars, these energetic objects shine brightly for a short while before dimming. They not only emit energy but also affect surrounding matter:

  • They can create ionized regions,
  • Blow bubbles in the interstellar medium,
  • Or even form enormous radio lobes stretching beyond their host galaxies.

Two years ago, a record was set when radio lobes from galaxy Alcyoneus extended 16 million light-years, the largest structure created by a single object. But now, a new galaxy, Porphyrion, has broken that record with its black hole-powered jets stretching an astonishing 24 million light-years, the largest known structure ever created by one object.

Credit: X-ray: NASA/CXC/CfA/R.Kraft et al Radio: NSF/VLA/Univ. of Hertfordshire/M.Hardcastle et al. Optical: ESO/VLT/ISAAC/M.Rejkuba et al.

Black hole jets aren’t uncommon. Most large galaxies have supermassive black holes at their centers, with masses millions or billions of times that of the Sun. Generally, these galaxies are quiet:

  • They aren’t merging,
  • They aren’t interacting with neighbors,
  • They aren’t consuming matter actively,
  • And they form stars at a slow, steady pace, dictated by the gas in their disks and halos.

This is typical for galaxies like the Milky Way and Andromeda. But galaxies don’t always behave this way. Mergers and interactions can trigger rapid star formation or cause matter to be drawn toward central black holes, activating them. These events were more common in the early universe.

Credit: NASA, ESA, S. Baum and C. O’Dea (RIT), R. Perley and W. Cotton (NRAO/AUI/NSF), and the Hubble Heritage Team (STScI/AURA)

Today, we see many active galaxies nearby, such as Messier 87, Centaurus A, and Hercules A, whose black hole jets stretch beyond their galaxies, emitting radiation across multiple wavelengths. These jets can grow larger than galaxies themselves. The largest galaxy, IC 1101, spans 6 million light-years, but that’s nothing compared to the 16 million light-years of Alcyoneus. Discovered in 2022 by Martijn Oei, this massive structure once seemed to be the upper limit for black hole jets.

In a first-of-its-kind image, the scale of galaxies, including the Milky Way, Andromeda, the largest spiral (UGC 2885), the largest elliptical (IC 1101), and the largest radio galaxy, Alcyoneus, are all shown together and, accurately, to scale.
Credit: E. Siegel

At the time, many didn’t believe jets could get larger. Theoretical models suggested 16 million light-years was the maximum due to factors like:

  • The amount of matter falling into the black hole,
  • The duration of the black hole’s active phase,
  • The density of the surrounding medium.

Yet, Porphyrion’s discovery, detailed in a September 2024 Nature paper, has proven otherwise. Oei, now a researcher at Caltech, found that Porphyrion’s jets stretch 24 million light-years—on the scale of the cosmic web itself. This challenges prior beliefs about how large cosmic jets can become and suggests that they play a bigger role in shaping the universe than previously thought.

While Alcyoneus’ jets were 30% the size of a cosmic void, Porphyrion’s are two-thirds that size. These jets, 140 times the diameter of the Milky Way, show that black hole jets can extend much further than anyone had imagined.

Credit: Erik Wernquist/Dylan Nelson (IllustrisTNG collaboration)/Martijn Oei; Design: Samuel Hermans

This discovery has huge implications for understanding the early universe. In the past, galaxy mergers, interactions, and gas infall were much more common, meaning black hole jets like Porphyrion’s may have been far more frequent. The universe was also smaller back then, suggesting that these jets could have influenced the formation of large-scale structures.

The power of Porphyrion’s jets is immense, estimated at around 1039 watts—more than two trillion times the Sun’s energy output and greater than the total energy from all the stars in the galaxy that hosts Porphyrion. The jets have likely been active for at least a billion years, a remarkably long time for a black hole to remain active.

The radio data from LOFAR and GMRT clearly shows the features of a coherent, bipolar, linear black hole pair of jets that extend for 23-24 million light-years in extent. This feature, named Porphyrion, is the largest black hole jet ever seen.
Credit: M.S.S.L. Oei et al., Nature, 2024

For jets to reach this size, they must pierce through several layers:

  • The medium surrounding the black hole,
  • The interstellar gas within the galaxy,
  • The circumgalactic medium that extends hundreds of thousands of light-years,
  • And finally, intergalactic space.

Typically, jets spread out over time, but Porphyrion’s have remained coherent for far longer than expected, showing that black hole jets can stay intact for extended periods.

By analyzing the energy and lifespan of Porphyrion’s jets, scientists can estimate how much the black hole has grown. It likely gained at least one billion solar masses during this time, starting at a size of one billion solar masses before the jets formed. The orientation of the black hole remained stable throughout this period, which is unusual for such long-lived systems.

The discovery of Porphyrion also changes our understanding of the intergalactic medium. Since jets like these were more common in the early universe, they may have played a significant role in magnetizing intergalactic space, which was previously thought to be influenced mainly by stars and early universe processes.

Now, black hole jets are being considered as a possible source of the intergalactic magnetic fields. Despite expectations that jets would destabilize over time, Porphyrion shows that they can remain coherent even when the universe was denser than it is today.

Whenever a new phenomenon is discovered, it raises questions about how common it might be. Porphyrion is the largest black hole jet system found, but others like it could exist, particularly in the distant universe where the conditions for their formation were more favorable.

Many active black hole jets, like those in BL Lacertae objects or blazars, are viewed face-on and appear extremely bright, but their size is hard to measure because of this perspective. These objects, seen by the JWST, are likely similar in energy to Porphyrion, but their jets remain a mystery.

The quasar-galaxy hybrid GNz7q is seen here as a red dot in the center of the image, reddened because of the expansion of the Universe and its great distance from us. Although it’s been exposed in the GOODS-N field for over 13 years, it was only flagged as an object of interest in 2022, as its spectrum reveals properties of both galaxy and quasar. These very distant, very red, but somehow very bright objects are common in JWST’s field of view. Many of the “little red dots” seen by JWST and other observatories are brightness-enhanced by the activity of the central black hole, with some jets pointing directly along our line-of-sight.
Credit: NASA, ESA, G. Illingworth (UCSC), P. Oesch (UCSC, Yale), R. Bouwens (LEI), I. Labbe (LEI), Cosmic Dawn Center/Niels Bohr Institute/University of Copenhagen, Denmark

Recent research has shown that black holes are more abundant and formed earlier in the universe than once believed. Now, it seems black holes can also stay active and emit powerful jets for much longer than expected, shaping the universe in ways we’re only beginning to understand.

But how common are systems like Porphyrion? To create one, a galaxy needs to undergo a major, prolonged merger, continuing to feed a supermassive black hole without disrupting it. This is a question for future research, which will require large-scale surveys in various wavelengths of light. With Porphyrion’s discovery, we now know what questions to ask about the connection between the growth of the universe and the supermassive black holes that influence it. The answers, however, will have to wait for more data.

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Jane
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Jane
1 month ago

This isn’t notable because there are plasma jets “blasting out;” that’s simply how certain types of black holes work.
What is notable is that these jets are much larger (7Mpc) than previous observations or predictions (4-5Mpc). At this larger scale, jets from supermassive black holes could play a significant cosmological role beyond their own galaxy, this paper theorizes.

Daniel
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Daniel
1 month ago

So like… in layman’s terms… the black hole farted?

Ozca
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Ozca
1 month ago
Reply to  Daniel

In layman’s terms, imagine that you’re taking a lime and pushing it up against the ‘surface’ of a sphere-shaped black hole.
As part of the lime enters the black hole, it gets crushed under immense force. That force also compresses bits of the lime still outside the black hole because it’s all connected. This means that the outer half of the lime ends up rupturing and splashing juice everywhere before getting sucked fully inside.
The plasma streams are the juice.

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