The giant Alcyoneus radio galaxy, located 3 billion light-years away, extends into space a distance of 5 megaparsecs. This is equivalent to about 16.3 million light-years, making the Alcyoneus galaxy the largest known cosmic object of galactic nature. This discovery highlights our lack of understanding of the nature of these cosmic "colossi" and what drives their growth to such incredible sizes.
Giant radio galaxies are another of the mysteries of the universe. They consist of the central galaxy, the usual cluster of stars orbiting the galactic nucleus. From the bowels of the central galaxy colossal jets are ejected into space, forming huge petals in space. These jets and petals, interacting with the intergalactic medium, work like an electron gas pedal, a synchrotron, resulting in intense radiation in the radio spectrum.The jets can travel enormous distances before they begin to scatter and form petals that emit radio waves.
This is quite a common process in the Universe; even the Milky Way has its radio petals. But what scientists have no explanation for is why some ordinary-looking galaxies have these petals growing to enormous sizes, counted in megapassecs, which is why such galaxies are called giant radio galaxies.
Let's return to the recently discovered radio galaxy Alcyoneus. It was found using an array of data collected by the LOFAR (LOw Frequency ARray) radio telescope, which includes approximately 20,000 antennas scattered across 52 locations in Europe and linked into a single network. The data was run through a filter to remove radio signals from compact sources that could interfere with detection of weaker signals from huge radio galaxy lobes.
And even after that, automation and software could not recognize anything interesting in the image, and the Alcyoneus galaxy was detected by using the most advanced pattern recognition tool in the world - the human eye and brain. Scientists then measured the size of the galaxy, which was 5.04 ± 0.05 megaparsecs.
Scientists believe that the reason for this phenomenon may be that the central galaxy of the Alcyoneus radio galaxy is located in a region of space in which the density of matter is much lower than the average value in the universe, which allows jets to spread over long distances without encountering resistance. Another explanation could be that the central galaxy is exactly at the point of a knot, where several strands of the cosmic universe network are intertwined.
Anyway, scientists believe that the Alcyoneus radio galaxy is still growing in size even now, but the rate of this process cannot be measured because of the great distance separating us and the long time it takes to make observations.