THE ALCYONEUS GALAXY
Astronomers just found the largest galaxy ever discovered, and they have no idea how it got so big.
At 16.3 million light-years wide, the Alcyoneus galaxy has a diameter 160 times wider than the Milky Way and four times that of the previous title holder, IC 1101, which spans 3.9 million light-years, researchers reported in a new study. Named after one of the mythical giants who fought Hercules and whose name means "mighty ass" in Greek, Alcyoneus is roughly 3 billion light-years from Earth.
The galactic monster is a particularly large example of a radio galaxy, or a galaxy with a supermassive black hole at its center that gobbles up enormous amounts of matter before spitting it out in the form of two massive jets of plasma moving at near-light speed. The plasma beams slow down after traveling millions of light-years, spreading out into plumes that emit light in the form of radio waves. The lobes of Alcyoneus are the largest ever discovered.
Galaxies with massive, plasma-filled radio lobes aren't uncommon (the Milky Way has two small plumes), but scientists are baffled as to how Alcyoneus, a relatively ordinary galaxy at its core, was able to grow such monstrously huge plumes.
Apart from its massive plumes, Alcyoneus is a typical elliptical galaxy, with a total mass roughly 240 billion times the mass of the sun (half that of the Milky Way) and a central supermassive black hole 400 million times the mass of the sun (100 times less massive than the largest black hole).
In fact, Alcyoneus' center is small in comparison to the centers of most radio galaxies.
