Highlights:
- Astronomers have discovered the longest black hole jet structure, named Porphyrion, stretching over 7 million parsecs (Mpc).
- This discovery challenges previous assumptions about the maximum size of black hole jets, previously thought to be limited to about 5 Mpc.
- The jets originate from an active galactic nucleus (AGN) fueled by a supermassive black hole (SMBH), revealing new insights into energy transport in the cosmic web.
- Porphyrion’s formation occurred between 4.4 and 6.3 billion years after the Big Bang, indicating these jets existed when the Universe was far denser than today.
TLDR:
A team of astronomers has discovered a record-breaking black hole jet structure, Porphyrion, spanning about 7 million parsecs. This discovery redefines our understanding of black hole jet growth and their role in shaping the Universe’s cosmic web.
Main Article:
Breaking the Limits of Black Hole Jet Growth
For over 50 years, scientists believed that the size of black hole jets could not exceed 5 million parsecs (Mpc). This limitation arose from both theoretical models and observational data. However, a recent study led by Martijn S. S. L. Oei from Leiden University and an international team of researchers has shattered this notion with the discovery of Porphyrion, a black hole jet structure that spans an astonishing 7 Mpc—about 66% of the radius of a cosmic void at its epoch.
Porphyrion is an outflow of particles and energy from a supermassive black hole (SMBH), forming the largest galaxy-made structure in the known Universe. This structure comprises a northern lobe, a northern jet, a core, a southern jet with an inner hotspot, and a southern outer hotspot with a backflow. These components combine to form a colossal system that extends beyond any previously observed black hole jets.
What Makes This Discovery So Important?
Black holes with strong jets have long been known to shape their environments by injecting energy and particles into the surrounding intergalactic medium (IGM). However, the scale of Porphyrion’s jets suggests that their influence may be far more extensive than previously believed. The jets reach across a large portion of the cosmic web, significantly impacting the distribution of matter and magnetism on a cosmic scale.
Such jets are crucial to understanding galactic evolution. The energy they pump into the IGM can affect galaxy formation, cluster development, and even the overall structure of the cosmic web. Porphyrion offers a rare glimpse into how black holes can influence the Universe at vast distances.
How Was Porphyrion Discovered?
The discovery of Porphyrion was made possible using radio images from the International LOFAR Telescope (ILT), which operates at a wavelength of 2.08 m. A combination of machine learning and citizen scientist efforts enabled researchers to identify the structure amidst extensive radio data. Follow-up observations were conducted using the upgraded Giant Metrewave Radio Telescope (uGMRT) at a wavelength of 0.46 m, confirming the size and details of the structure.
Unlike previously discovered megaparsec-scale jets, Porphyrion stands out due to its thin and elongated shape, as seen in radio observations. The structure also appears to be unusually straight, suggesting that it has avoided significant magnetohydrodynamical instabilities, such as the Kelvin–Helmholtz instability, that typically disrupt jets over such long distances.
Porphyrion’s Black Hole Origins
The team used data from the ILT to pinpoint the origin of Porphyrion’s jets. This process revealed that the jets likely emanate from a supermassive black hole in a galaxy that is actively accreting material, categorized as a radiatively efficient AGN (RE AGN). This type of AGN efficiently converts gravitational energy from infalling matter into radiation, making it a highly luminous source in the Universe.
Interestingly, all previously known record-length outflows were fueled by radiatively inefficient AGN (RI AGN), making Porphyrion unique in both its length and the nature of its energy source. The researchers obtained a spectroscopic redshift (z = 0.896 ± 0.001) using the Low Resolution Imaging Spectrometer (LRIS) on the W. M. Keck Observatory. This redshift measurement indicates that Porphyrion originated about 6.3 billion years after the Big Bang, a time when the Universe was still significantly denser than it is today.
What Makes Porphyrion So Special?
The discovery of Porphyrion challenges current theories about black hole jet longevity and stability. Jets are expected to be disrupted by instabilities and mass entrainment from the IGM, especially in denser regions of the early Universe. However, Porphyrion demonstrates that jets can remain collimated over cosmological distances, even in epochs when the Universe was up to 15 times denser than it is today.
The power of Porphyrion’s jets was estimated at about 1.3 × 10³⁹ W, with an age of approximately 1.9 billion years. This level of energy is comparable to that released during galaxy cluster mergers, making it one of the most energetic events in its cosmic web region.
Implications for Our Understanding of the Cosmic Web
The cosmic web is a vast network of galaxies, gas, and dark matter that forms the large-scale structure of the Universe. Black hole jets, like those seen in Porphyrion, play a critical role in distributing energy, cosmic rays, and magnetic fields throughout this web.
The discovery of Porphyrion suggests that RE AGNs, which were more abundant in the early Universe, could have been far more effective in transporting energy across the cosmic web than previously understood. This finding implies that black hole jets may have been instrumental in shaping the Universe’s evolution, especially during its formative years.
What’s Next for Research on Black Hole Jets?
This discovery opens up numerous avenues for further research. How do jets maintain coherence over such vast distances? What impact do they have on the thermal history of the IGM and the formation of large-scale structures? Answering these questions will require more detailed observations and theoretical models, potentially leading to an even deeper understanding of the role of black holes in the cosmos.
Source:
Oei, M. S. S. L., et al. (2024). Black hole jets on the scale of the cosmic web. Nature, 633, 537-541. https://doi.org/10.1038/s41586-024-07879-y