Astronomers have discovered the largest known galaxy 153 times the size of our Milky Way, the galaxy called Alcyoneus, which is about 3 billion light-years from Earth and about 16.3 million light-years long. By comparison, the Milky Way is just under 106,000 light-years long.
According to the British newspaper "Daily Mail", Alcyoneus has been identified as a giant radio galaxy, and contains a host galaxy along with huge jets and lobes erupting from its center.
Little is known about these mysterious radio galaxies, but experts believe that the jets and their associated lobes are a byproduct of an active supermassive black hole in the galactic center.
A black hole is known to be "active" when it eats matter from a giant disk of material around it, however, not all of this material ends up beyond the black hole's event horizon, because a small portion is directed from the inner region of the disk to the poles, where it is pushed into the Space in the form of batches of ionized plasma.
These jets are able to travel great distances at the speed of light, before scattering through giant radio-lobes, and despite the size of Alcyoneus, the type of radio-lobes they emit are not far from uncommon. It is also known that our Milky Way has its own radio lobes.
But one of the most mysterious things about Alcyoneus and other massive galaxies like it is how they grow so large, and researchers led by the Leiden Observatory in the Netherlands hope their discovery of the galaxy will help shed light on how radio galaxies form and why they are so big.