An international group of researchers working on astrophysics explained that the difference in composition between the plasma may be responsible for the variations in structure of extragalactic jets emitted from the regions surrounding supermassive black holes.
This study was published in a scientific publication called The Astrophysical Journal based on the computer simulations conducted by researchers from Aryabhatta Research Institute of Observational Sciences (ARIES), Presidency University, the Nicolaus Copernicus Astronomical Center, and Mahatma Jyotiba Phule Rohilkhand University. In the current study, scientists investigated the impact of the plasma amount fluctuations on the characteristics of relativistic jets.
The process called extragalactic jets is related to the energy and particle flow from the region of supermassive black holes inside galaxies. These jets extend up to thousands of light-years in length, emitting radiation throughout the whole spectrum.
Scientists have traditionally categorized jets into two types based on their characteristics at radio wavelengths — FR I and FR II. In an FR I jet, brightness peaks near the galaxy’s center, fading outward, whereas an FR II jet is confined to a narrow channel until it culminates in a hotspot.
There has been much speculation about why the jets display different structures since the 1960s. Earlier explanations attributed the difference to the nature of the black hole, the environment around it, or the jet itself, including velocity and magnetic field intensity.
According to the study, plasma composition may play a significant role in determining how jets evolve. Researchers used three-dimensional magnetohydrodynamic simulations to model jet behaviour over large distances.
The simulations showed that jets containing higher proportions of positrons — the antimatter counterpart of electrons — tended to remain hotter and expand more rapidly. These jets were more vulnerable to a process known as “kink instability”, in which bends or distortions grow within the jet structure. As the instability increases, the jet loses its narrow form and spreads into diffuse clouds resembling FR I-type jets.
In contrast, jets composed mainly of electrons and protons were found to maintain more stable structures for longer periods and could transition between jet morphologies over time.
The researchers said the findings may help improve understanding of the matter composition of relativistic jets and their long-term evolution. They also suggested that observations captured through telescopes could represent different stages of an ongoing cosmic process rather than fixed categories of jet structures.
The study used a numerical simulation framework developed by ARIES that incorporates relativistic equations of state to model temperature changes across different jet regions.
