It is true that gargantuan structures exist in our Universe, but these are usually very large collections of black holes or galaxies. Recently, however, the largest galaxy ever was observed: Alcyoneus, 16.3 million light years longas well as the largest structure of galactic origin.
These ‘giant’ formations remain a mystery: they consist of a host galaxy (the cluster of stars orbiting a galactic nucleus containing a supermassive black hole) and colossal jets and lobes erupting from the galactic center. These jets can travel enormous distances before expanding into giant lobes that emit radio waves.
It’s not a strange thing, mind you. Even the Milky Way (our home) has similar jets. The strange one, which we don’t have much control over, is that some galaxies grow to absolutely gigantic sizes, on megaparsec scales. To find the new discovery, the astronomers looked for these “outliers” in data collected by the LOw Frequency ARray (LOFAR), an interferometric network made up of around 20,000 radio antennas, spread across 52 locations across Europe.
That’s how they found Alcyoneus a few billion light years away. The cosmic structure has a mass of approx 240 billion times that of the Sun it’s a supermassive black hole in the center about 400 million times the mass of the Sun. Alcyoneus may be in a region of space with a lower than average density, which could allow it to expand, or interaction with the cosmic web plays a role in the object’s growth.
What is certain is that the galaxy is expanding more and more and we have not understood why.