The Milky Way, the galaxy in which we live, doesn't appear particularly peculiar. Moderately large, spiral-shaped, and with a few kinks that allude to a turbulent history.
But scientists have lately discovered a peculiarity that has never been observed in any galaxy that has been examined to date: the Milky Way is too large for its surrounds.
In particular, it looks to be overly big for the Local Sheet community in which it is located. This flattened arrangement of galaxies has comparable velocities and is surrounded on both sides by voids, which are essentially empty spaces.
As an illustration of a "cosmological wall," our Local Sheet divides the Local Void from the Southern Void in one direction.
Due to, for instance, their comparable velocities in respect to the expansion of the Universe, the interaction between the galaxies in the Local Sheet appears to have a significant impact on how they behave. These velocities would have a far greater range if they weren't restricted by the cosmic wall environment.
A team of astronomers led by Miguel Aragón of the National Autonomous University of Mexico performed an investigation utilising simulations from a project called IllustrisTNG, which simulates the physical Universe, to ascertain the impact the environment has on the galaxies around us.
They didn't anticipate discovering anything really unusual.
In a way, the Milky Way is unique, explains Aragón. "Earth is definitely unique since it is the only known place where life exists. However, neither the Solar System nor the entire Universe are in its core. There are billions of stars in the Milky Way, and the Sun is just one of them. Even our galaxy appeared to be no different from the billions of other spiral galaxies in the visible Universe."
A different image, however, emerged when scientists simulated a region of space approximately a billion light-years across and containing millions of galaxies: only a small number of galaxies as enormous as the Milky Way could be found within a cosmic wall structure.
"There is no especially unique mass or kind of the Milky Way. There are several spiral galaxies that resemble it "claims astronomer Joe Silk of the Institut d'Astrophysique de Paris at the Sorbonne University in France.
"However, if you consider its surroundings, it is unusual. You would see that they all almost lie on a ring, embedded in the Local Sheet, if you could readily view the nearest dozen or so massive galaxies in the sky. That in and of itself is somewhat unique. We recently discovered that other barriers of galaxies in the Universe, such as the Local Sheet, seldom ever appear to contain a galaxy as large as the Milky Way."
The biggest galactic neighbour of the Milky Way, Andromeda, was not included in the team's investigation. It is a galaxy that is similar in size to the Milky Way and is a feature of the Local Sheet, making it a component of the same cosmic wall. Their findings still hold true since two heavyweights in a cosmic wall would be far more uncommon.
The research does, however, point out that, rather than assuming that our home hangs out in an average fashion in an average position in the Universe, we might need to consider our local environment while studying the Milky Way.
Future studies could take into account other galaxies in the Local Group as the team's simulations only took into consideration the Milky Way's surroundings inside a cosmological wall. Additionally, the strange arrangement of satellite galaxies surrounding Andromeda and the odd absence of them near the Milky Way might also be explained by the environmental background, according to the researchers.
Choosing features that are considered "unique" requires caution, according to astronomer Mark Neyrinck of the Basque Foundation for Science in Spain.
"We would unquestionably be the only galaxy in the observable Universe if we imposed an absurdly onerous requirement, like the requirement that the galaxy contains the article we authored about it. However, we believe that this "too huge for its wall" quality is physically significant and observably relevant enough to be called out as truly unique."
Under the terms of a Creative Commons licence, this article has been taken from science alert. Go here to read the original article.
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