The radio lobes of Alcyoneus. (Oei et al., arXiv, 2022)

The revelation demonstrates our lack of understanding of these colossi and what causes their phenomenal development. However, it may pave the way to a deeper knowledge of not only mᴀssive radio galaxies but also the intergalactic medium that floats in the vast gaps of space.

Giant radio galaxies are just one more enigma in a Universe full of mysteries. They are made up of a host galaxy (a cluster of stars around a galactic nucleus containing a supermᴀssive black hole) and huge jets and lobes that erupt from the galactic core. When these jets and lobes contact the intergalactic medium, they operate as a synchrotron, accelerating electrons that emit radio emissions.

Three images of the largest galaxy ever discovered by astronomers in infrared, radio, and optical wavelengths. The galaxy in question Alcyoneus, spans a whopping 16.3 million light years. MARTIJN SIMON SOEN LIONG OEI/LOFAR

Astronomers found Alcyoneus after processing the data collected by the LOw Frequency ARray (LOFAR) in Europe. The astronomers, responsible for this discovery, wrote: “We have discovered what is in projection the largest known structure made by a single galaxy – a giant radio galaxy with a projected proper length [of] 4.99 ± 0.04 megaparsecs. The true proper length is at least … 5.04 ± 0.05 megaparsecs,”

Astronomers believe that Alcyoneus is still growing even bigger, far away in the cosmic dark. The research has been accepted for publication in Astronomy & Astrophysics, and is available on arXiv. 

You can read more about this discovery here.