October 23, 2024
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Is it possible that giant black hole jets shaped the early universe?
Supermassive black holes can emit jets of matter so vast and powerful that they can shape the large-scale structure of the universe
Artist’s illustration of the longest black hole jet system ever observed. Nicknamed Porphyrion after the Greek mythological giant, these jets span approximately 7 megaparsecs, or 23 million light-years. This is equivalent to lining up 140 Milky Way galaxies back to back.
E. Wenquist/D. Nelson (IllustrisTNG collaboration)/M. Oei (CC BY-NC-ND)
In a galaxy 7.5 billion light years away, a supermassive black hole spews a stream of magnetized plasma the length of the 140 Milky Way. The astonishing structure, called a porphyrion after the Greek mythological giant, contains the largest black hole jet physicists have ever seen, a team of researchers announced. reported in nature last month. And their existence suggests that black hole jets may have played a more important role in the formation of the universe than previously thought.
When a black hole eats too much food, it can generate jets as material builds up around its mouth and encounters extreme astrophysical forces. All matter that approaches a black hole takes the form of a spiral disk. This disk rotates at such a fast pace that the matter inside it becomes white-hot and ionized, turning into a dense plasma with swirling magnetic fields. A rotating black hole can twist these magnetic fields into a tight cone shape at each of its rotating poles. Most matter leaving the disk accelerates straight toward the mouth of the black hole. But instead, a small portion is trapped in a twisted field that slingshots outward, producing two straight beams that some astrophysicists liken to a Jedi lightsaber.
Such jets initially attracted the attention of scientists because they served as visual markers of black holes, bottomless pits that are invisible to most telescopes. Over time, researchers came to realize that jets are important in their own right. The intense heat produced by the jet stream can prevent the surrounding gas from collapsing and forming new stars. However, such effects appeared to be limited, as the jets were not thought to extend very far, if at all, beyond the reach of the Milky Way. The sky survey that forms the basis of the new study complicated the situation by identifying more than 10,000 giant black hole jet systems, the majority of which were found to be porphyrions.
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Streams as old and massive as porphyrions may have contributed to some of the features of the early universe, said study lead author Martin Oei, an astronomer at the California Institute of Technology.
In 2022, Daiei and his research colleagues discovered another jet system spewing a black hole that spans 16 million light years from end to end, or 100 Milky Ways. Porphyrion surpasses this previous record holder, Alcyoneus, not only in its absolute size, but also in its relative influence over its cosmic surroundings. Born when the universe was less than half its current age and therefore much smaller and denser than it is now, Porphyrion can reach out and touch more things than Alcyoneus.
Porphyrion’s jet contains the combined force of trillions of suns and is estimated to raise the temperature of the surrounding gas by a million degrees Celsius. This means that it may have prevented the formation of not just stars but entire galaxies in the early Universe. Their high-velocity sprays of magnetized ejecta may also have pierced and filled voids in the cosmic web, a network of matter-rich filaments and matter-poor cavities that make up the large-scale structure of the universe.
What excites Daiei most is the possibility that jet systems like Porphyrion helped set the stage for life on Earth. Our planet’s magnetic field protects Earth’s biosphere and atmosphere from barrages of high-energy cosmic rays and dangerous bursts of solar particles and radiation. But the Earth’s magnetic field itself is embedded in, and thus interconnected with, our star’s magnetic field, and that field exists in other magnetic fields that extend further across the Milky Way and perhaps beyond. I will. The trajectory of this scalar is long and thin, but it can be traced back through space and time to our own perches in the threads of the cosmic web or to potential perturbations by structures like porphyrions.
To better assess the impact such jets may have had on the early universe, researchers need to create a more comprehensive catalog of structures. The new study explores just 15% of the sky, and there may be many more jets yet to be discovered. And because the conditions that create and sustain powerful rivers are not yet well understood, it’s difficult to estimate how many of these giant structures exist, Oei points out.
That scientists can see even such large jets is a testament to the sensitivity of modern telescopes. Because of the jet’s very large size, it is difficult to detect it with the narrow field of view available from most suitable powerful telescopes. In the new study, Daiei and his team focused on a network of radio telescopes in Europe called the Low Frequency Array (LOFAR), searching for radio light at wavelengths of about 2 meters in its images of the sky. These “human-sized waves” signaled “a place where something violent and spectacular was about to happen,” he said. When Porphyrion emerged, they used two other facilities, the Giant Meter Radio Telescope in India and the W. M. Keck Observatory in Hawaii, to discover and study the galaxy that was the source of the signal. Daiei, who initially started researching the web of the universe, realized that Porphyrion’s two jets were doubly surprising. Countless more are expected as the team continues to study Porphyrion and other giant jet systems.
