Alcyoneus (galaxy)
Alcyoneus is a radio galaxy located around 3 billion light years away in the constellation Lynx, discovered using the Low-Frequency Array (LOFAR) network. At around 5 million parsecs (16.3 million light years) wide, its radio lobes are the largest known structure made by a single galaxy. The host galaxy, SDSS J081421.68+522410, also contains a supermassive black hole weighing million solar masses. Aside from the size of its radio emissions, the galaxy is otherwise of ordinary radio luminosity, stellar mass, and supermassive black hole mass. It is a standalone galaxy, with the nearest cluster located 11  million light years away from it. It was named after Alcyoneus, one of the opponents of Heracles in Greek mythology. It is currently unknown how Alcyoneus's radio emissions grew so large. A few theories have been proposed, including a lesser dense than usual environment surrounding it, the fact that it exists inside a filament of the cosmic web, a supermassive black hole, an extensive stellar population, and powerful jet streams.