The Largest Galaxy Ever Seen Has Just Been Discovered

Astronomers have just discovered an absolute beast of a galaxy

Hiding some 3 billion light-years away, Alcyoneus is a giant radio galaxy reaching five megaparsecs into space. That is 16.3 million light-years long and represents the biggest recognized structure of galactic origin.

The finding highlights our poor understanding of these colossi and what drives their extraordinary growth. It might supply a path to far better understanding, not just of giant radio galaxies but the intergalactic medium that wanders in the yawning voids of space.

Giant radio galaxies

Giant radio galaxies are yet another enigma in a Universe packed with enigmas. They consist of a host galaxy (that is, the collection of stars orbiting a galactic nucleus containing a supermassive black hole), in addition to colossal jets and lobes that emerge forth from the galactic center.

Engaging with the intergalactic medium, these jets and lobes work as a synchrotron to accelerate electrons that produce radio emissions.

We are pretty sure we know what generates the jets: an active supermassive black hole at the galactic. We describe a black hole as ‘active’ when it is guzzling down (or ‘accreting’) material from a giant disk of material around it.

How do giant radio galaxies behave?

Not all the material in the accretion disk whirling into an active black hole inevitably winds up beyond the event horizon. A little portion of it in some way gets funneled from the inner area of the accretion disk to the poles, where erupts into space in the form of jets of ionized plasma, at speeds a considerable percentage of the speed of light.

These jets can voyage huge distances prior to spreading out into giant radio-emitting lobes.

This process is quite regular. Also, the Milky Way has radio lobes. We do not truly have a great handle on why, in some galaxies, they expand to completely colossal sizes on megaparsec scales. These are named giant radio galaxies, and the most extreme instances could be crucial to understanding what drives their expansion.

” If there exist host galaxy characteristics that are an essential trigger for giant radio galaxy expansion, after that the hosts of the biggest giant radio galaxies are most likely to have them,” the researchers, led by astronomer Martijn Oei of Leiden Observatory in the Netherlands, detail in their preprint paper, which has actually been accepted for publication in Astronomy & Astrophysics.

” Similarly, if there exist specific large-scale environments that are extremely conducive to giant radio galaxy expansion, after that the biggest giant radio galaxies are likely to reside in them.”.

The team’s research

The group went searching for these outliers in data collected by the Low Frequency Array (LOFAR) in Europe. The LOFAR is an interferometric network composed of approximately 20,000 radio antennas distributed throughout 52 locations all over Europe.

They reprocessed the data through a new pipeline, eliminating compact radio sources that could hinder detections of diffuse radio lobes and fixing for optical distortion.

The resulting photos, they claim, represent the most delicate search ever performed for radio galaxy lobes. They used the finest pattern recognition tool available for situating their target: their own eyes.

This is how they discovered Alcyoneus, gushing forth from a galaxy a few billion light-years away.

” We have actually identified 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 the very least … 5.04 ± 0.05 megaparsecs,” they write.

Once they measured the lobes, the researchers utilized the Sloan Digital Sky Survey to try to understand the host galaxy.

They found that it is a fairly normal elliptical galaxy, implanted in a filament of the cosmic web, appearing at approximately 240 billion times the mass of the Sun, with a supermassive black hole at its center approximately 400 million times the mass of the Sun.

Both of these parameters are at the low end for giant radio galaxies, which can supply some clues regarding what drives the expansion of radio lobes.

” Beyond geometry, Alcyoneus and its host are suspiciously plain: the total low-frequency luminosity density, stellar-mass, and supermassive black hole mass are all less than, though comparable to, those of the medial giant radio galaxies,” the scientists write.

” Thus, really enormous galaxies or central black holes are not essential to grow big giants, and, if the observed state represents the source over its lifetime, neither is high radio power.”.

Maybe Alcyoneus is resting in a region of space that is lower density than average, which could enable its growth– or that interaction with the cosmic web contributes to the object’s growth.

Whatever is behind it, though, the scientists believe that Alcyoneus is still growing even more, far away in the cosmic dark.

The research has been accepted for publication in Astronomy & Astrophysics and is available on arXiv.

Read the original article on Interesting Engineering.

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