The largest jets expelled from a black hole ever observed to date

Gargantuan. This is the word chosen by American and European astrophysicists to describe their most recent discovery: a pair of plasma jets escaping from a black hole over a length of 23 million light years.

By comparison, their common length is equivalent to lining up 140 galaxies of a diameter similar to the Milky Way one after the other.

These are, unsurprisingly, the longest jets observed to date escaping from a black hole.

The Milky Way would correspond to a small point in these two giant eruptions, notes Martijn Oei, astrophysicist associated with California Institute of Technology (CALTECH) and lead author of the discovery described in the journal Nature (New window) (in English).

According to its discoverers, the megastructure of jets named Porphyrion – after the giant of Greek mythology – dates from a time when the Universe was 6.3 billion years old, half its current age of 13.8 billion years.

This work is important, since it tells us about the history of the Universe, but also about how galaxies form and evolve over time. And they represent a surprise, because most active galaxies are observed in the nearby Universesays Marine Prunier, doctoral student in astrophysics at the University of Montreal, who did not participate in the work.

There are extremely old galaxies that already have supermassive black holes at the beginning of the Universe. And very big ones. It’s very mysterious!

More sightings

The Porphyrion jet system was discovered during a survey of the sky carried out with the European LOFAR (LOw Frequency ARray) radio telescope which has revealed more than 10,000 faint megastructures so far.

Hundreds of large jet systems had been detected before the observations of PROMISESbut these were on average much smaller than the thousands of systems discovered using the radio telescope.

Before this discovery, the largest jet system detected was Alcyonea, also named after a giant from Greek mythology. This system discovered in 2022 by the same team extends over the equivalent of a hundred galaxies the size of the Milky Way.

By comparison, the large Centaurus A jet system, closest to Earth, extends over around ten galaxies with a diameter equivalent to the Milky Way.

Mysterious structures

While scientists still don’t know for sure how supermassive black holes are created, mergers of other types of black holes could be their origin.

The phenomenon of jets is not very well understood either, but we still have some cluesremarks Marine Prunier.

You should know that a black hole accretes matter and gas found in its environment. These two elements end up rotating around it and creating what is called an accretion disk which heats up and emits light.

The rotation of this accretion disk is thought to create strong magnetic fields that eventually create perpendicular jetssummarizes Marine Prunier.

Apparently, the black hole causing the duo of jets is in a very dense location where there are only a few galaxies orbiting each other.

But usually, black holes with jets are observed in much larger galaxy clusters, and where there are several thousand galaxies orbiting each other in a less dense environment.

Effects on the cosmic web

The authors of this work believe that galaxies and their central black holes evolve together. And the jets there would radiate enormous amounts of energy that affect the growth of their host galaxies and other nearby galaxies.

In addition, the discovery of the celestial duo gargantuan suggests that giant jet systems may have had a greater influence on the formation of galaxies in the young Universe than previously thought.

What is particularly interesting about this work is that it shows the significant effect of these jets on the cosmic web. The activity of a single black hole could therefore have effects on extremely large scales, perhaps affecting the very evolution of the Universe.notes Marine Prunier.

The authors of the work explain that Porphyrion existed at a time when the filaments that connect and power galaxies, known as the cosmic web, were closer together than they are today.

This probably means that the gigantic jets covered a larger part of the cosmic web than the current jets observed from the local Universe.

The doctoral student explains that the jets emitted by black holes heat the galactic environment around them, which prevents the creation of new stars. Galaxies that have black holes with jets are older and usually form few stars. They say they are dying a littlesays Marine Prunier.

If we had a jet like these at the center of our Milky Way, a spiral galaxy that forms many stars, it would certainly accelerate its aging towards a more elliptical galaxynotes the doctoral student.

But as nothing is simple, a more local jet phenomenon could lead to the creation of stars at its end by compressing the gas and creating clouds which, by collapsing on themselves, would form stars.

Question loading

A hypothesis to refine

Additionally, observations made using the WM Keck Observatory show that Porphyrion emerges from what is known as an active black hole in radiative mode, as opposed to a black hole in jet mode.

You should know that when supermassive black holes activate – when their gravitational forces act on surrounding matter and heat it – they emit energy in the form of radiation or jets.

The researchers estimated that black holes in radiative mode were more common in the young Universe, while black holes in jet mode would be more common in the current Universe.

However, the fact that Porphyrion comes from a black hole in radiative mode also surprises astronomers, who did not know that this mode could produce such enormous and powerful jets.

Additionally, because Porphyrion is in the young Universe where radiative-mode black holes abound, this discovery implies that there could be many more colossal jets yet to be discovered.

We may only be seeing the tip of the icebergindique Martijn Oei.

Our study carried out with PROMISES only covered 15% of the sky. And since most of these giant jets are probably hard to spot, we suspect there are plenty more of these behemoths in the sky.

Regardless, astrophysicists still don’t understand how jets can extend so far beyond their host galaxies without destabilizing.

In future work, the authors wish to better understand how these megastructures influence their environment.

They want to try to determine to what extent the giant jets propagate magnetism.

The magnetism present on our planet allows life to develop, which is why we want to understand how it appeared.

We know that magnetism permeates the cosmic web, then makes its way into galaxies and stars, and finally onto planets, but the question is where it starts. Did these giant jets spread magnetism throughout the cosmos? he asks himself.

The first ever direct image of a matter ejection from a black hole was obtained in November 2022.