The universe is fantastic, exciting, and mind-blowing. It contains unimaginable structures and phenomena for our minds to fully comprehend, from a birth of a star and its planetary nursery to the jolt of space-time resulting from the black holes merging. Moreover, the distances and sizes are so immense that we can hardly perceive their dimensions. The perfect example would be the radio galaxy Alcyoneus, measuring 16 million light-years across; it is the largest galactic structure we have ever observed.
The science and other stuff to know
Giant radio galaxies, or GRGs, are the largest astrophysical entities in the cosmos. These galaxies harbor an active supermassive black hole that is actively accreting material. When it devours stars or the surrounding gas and dust, part of that material is directed toward the poles of the black hole, where it is ejected with great speed what we know as a relativistic jet. These jets form two lobes where gas from the environment near the black hole is deposited and accumulated, forming the giant radio galaxies that astronomers observe in astonishment.
The name radio galaxy refers to these structures’ characteristic x-ray emission. “Giant” refers to its colossal size. Their size varies from a few parsecs to several megaparsecs (1 megaparsec = 3.25 million light-years), according to the Nature Astronomy Community.
Alcyoneus is a GRG located in a far corner of the cosmos, 3.5 billion light-years away from us, and has thrilled experts with its enormous size — 5 megaparsecs (16 million light-years). To give us an idea of how ridiculous this number is, let’s consider that our Milky Way galaxy has a diameter of 100,000 light-years. It would take 30 Milky Ways lined up to equal one megaparsec, or 150 to equal the size of Alcyoneus.
The article detailing the finding of this GRG was published in Astronomy & Astrophysics and laded by Martin Oei. The team explained the procedure by which they found this source of x-ray emission and identified it as a GRG in the publication.
The astronomers involved in the research still do not understand how Alcyoneus came to grow in such an absurdly huge way. Also, its host galaxy doesn’t seem too outlier; it presents standard lightness and density values.
“Geometry beyond, Alcyoneus and its host are suspiciously ordinary: the low-frequency total luminosity density, stellar mass, and supermassive black hole mass are lower than those of medial giant radio galaxies, though similar. Therefore, massive galaxies or central black holes are not necessary for large giants to grow and, if the observed state is representative of the source during its lifetime, neither is high radio power,” the researchers suggest.
The article concludes by suggesting that the environment in which this GRG lives could be responsible for its growth: The Cosmic Web filament in which Alcyoneus is found could have a significant thermodynamic interaction. “The pressures in the lobes are the lowest found so far, and therefore Alcyoneus represents the most promising radio galaxy yet to explore the warm-hot intergalactic medium,” they conclude.