Supermassive black hole-powered blazar breaks record for most distant object of its kind ever found
Scientists have just confirmed finding the most distant blazar to date. Designated OP 313, this blazar is located about 8 billion light-years away, and it has pushed the boundary of how far we can see back in time. Blazars are extremely bright active galactic nuclei—regions at the center of galaxies that are powered by a supermassive black hole. They emit enormous amounts of high-energy gamma-ray jets, and they appear extremely bright when one of these jets directly face Earth.
OP 313 is classified as a flat-spectrum radio quasar, which is amongst the brightest and most powerful sources of radiation in the universe. The gamma rays from the blazar were discovered back in December 2023, but scientists decided to carry out more observations using the Large-Sized Telescope (LST-1) prototype and the Major Atmospheric Gamma-ray Imaging Cherenkov (MAGIC) telescope in Spain. Axel Arbet-Engels, a research fellow in the Department of Astronomy at the University of Geneva (UNIGE) and one of the corresponding authors of the study, explains that the gamma rays from OP 313 left once the universe had calmed down after a period of intense activity known as the 'cosmic noon.'
“Around 11 billion years ago, the universe experienced a period of peak activity known as the ‘Cosmic noon’, characterised by an intense rate of star and galaxy formation,” Arbet-Engels said in a statement. “When this phase of intense activity slowed down and galaxies began to evolve and mature, the Universe entered a calmer phase, which continues to this day.” OP 313 is said to have erupted at the start of this calmer phase, and an intense burst of gamma jets was released. These jets, the researchers say, were created by the supermassive black hole, which launched a jet of high-speed plasma containing electrons that are accelerated nearly to the speed of light. “Upon colliding with lower-energy photons surrounding the black hole, the electrons transfer part of their considerable energy to these photons, thereby propelling them to energy levels corresponding to very high-energy gamma rays,” explained Domenico Della Volpe, a professor in the Department of Nuclear and Particle Physics at UNIGE, and co-author of the paper.
But detecting these gamma rays is a monumental task because they have very short wavelengths and they lose energy upon collision with extragalactic background light or EBL. This background light is a field of radiation including light emitted from all the stars and galaxies and other cosmic objects that have ever existed. When the high-energy gamma rays collide with low-energy photons, their energy is converted into an electron-positron pair, and eventually the signal weakens over vast distances. But thanks to sensitive instruments like the LST-1 and MAGIC telescopes, scientists were able to determine how dense the EBL is and variability in the blazar’s brightness.
The findings, which have been published in the journal Astronomy and Astrophysics, also show the incredible observational capabilities of the LST-1 which is currently in the commissioning phase. On October 15, three more telescopes will be inaugurated and together they will form the complete LST sub-array at the Cherenkov Telescope Array Observatory (CTAO) on La Palma, Spain. Once ready, these telescopes will allow scientists to peer further back in time.
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