Recently scientists discovered the largest galaxy ever and discovered by astronomers. This galaxy is 153 times the size of the Milky Way, our galaxy. This galaxy is called Alcyoneus. Scientists claim, this galaxy is about 3 billion light years from Earth and about 16.3 million light years in length. In comparison, the Milky Way is just under 106,000 light-years across. Alcyoneus has been identified as a giant radio galaxy, and contains a parent galaxy along with a large jet and lobe erupting from its center. Little is known about this mysterious radio galaxy, but experts believe that the emission and the lobes associated with it are a by-product of an active supermassive black hole at the center of the galaxy. A black hole is defined as 'active' when it eats up, or 'boosts', material from the giant disk of material around it. However, not all of this material ends up outside the event horizon, as a small portion is funneled from the interior of the disk to the poles, where it is blasted out into space in the form of jets of ionized plasma. These jets are capable of traveling great distances at the speed of light, before spreading out into the giant radio-transmitting lobes. Despite Alcyoneus' size, the type of radio lobe he emitted was not extraordinary. Our Milky Way is also known to have its own radio lobe. But one of the most mysterious things about Alcyoneus and the other great galaxies is how they grew so big. Researchers led by the Leiden Observatory in the Netherlands hope their discovery of Alcyoneus can help explain how radio galaxies form and why they are so large.
"If there is a host galaxy characteristic that is an important cause for the growth of radio giant galaxies, then the host of the largest radio giant galaxy will likely have it," said Martijn Oei, of the Leiden Observatory.
"Similarly, if there is a certain large-scale environment that is very conducive to the growth of radio giant galaxies, then the largest radio giant galaxy will likely be within it," added Oie.
Oei and his team discovered this largest galaxy while looking for outliers in data compiled by the Low Frequency Array (LOFAR) in Europe. LOFAR consists of approximately 20,000 radio antennas, spread over 52 locations across continents. The researchers had to remove the compact radio source from the images to help detect the radio lobes and correct for optical distortion, which in turn led them to Alcyoneus. According to the astronomers involved in the study, the largest known galaxy is surrounded by a cosmic web more than 240 billion times the mass of the sun. They also think the supermassive black hole at the center of Alcyoneus is about 400 million times the mass of the sun. While those two parameters sound huge, they actually fall under for giant radio galaxies.
"Outside of geometry, Alcyoneus and its host are very unremarkable: the total low-frequency luminosity density, stellar mass, and supermassive black hole mass are all lower, although similar to medial giant radio galaxies," they wrote in their report.
"Thus, very massive galaxies or central black holes are not required to grow large giants, and, if the observed circumstances represent a source over their lifetime, neither is high radio power," the report adds.
The researchers hope their research will help astronomers learn more about how radio galaxies originated, how much Alcyoneus can grow and at what rate, and whether galaxies bigger than that are still out there.
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