The history of astronomy has been all about recognizing that our place in the universe isn’t all that special. We’ve gone from the center of all existence to just another planet orbiting an average star in one of billions and billions of galaxies. It turns out there might be something special about our galaxy, though. A new simulation suggests that the Milky Way is far larger than it should be based on the size of the “cosmological wall.”
The “wall,” in this case is more properly known as the Local Sheet. This is a region of extragalactic space occupied by the Milky Way and the other members of the Local Group. The Milky Way and other galaxies in this region share a similar velocity and are bordered by voids that are largely empty, seemingly compressing them into a sheet-like structure. Researchers from the IllustrisTNG project created a new simulation of the universe covering almost 1 billion light years.
This model showed something unusual. While the Milky Way isn’t even close to the largest galaxy in the universe, it’s actually enormous compared with the Local Sheet. The team used the IllustrisTNG simulation (TNG300) to search the known universe for other galaxies with the same relative beefiness compared with their Local Sheet. And you know what, we might be kind of special after all.
The study shows that “Milky Way analogs” are exceedingly rare. To find another galaxy that is similarly outsized for its Local Sheet, you’d have to travel 160–200 megaparsecs (one megaparsec is 3,260,000 light years). “So the Milky Way is, in a way, special,” said research lead Miguel Aragón. It’s an interesting distinction — taken alone, the Milky Way is as typical and uninteresting as the sun. It’s the way it interacts with its surroundings that makes it unusual.
We don’t know what this property of the Milky Way means in the grand scheme — maybe it’s nothing important. However, the team suggests that we should be aware of the so-called “Copernican bias,” which could lead us to assume that we live in a completely average and uninteresting place. That’s been the trend as we learn more about the universe, but the team believes the size of the Milky Way relative to the cosmological wall is physically and observationally relevant enough that it deserves to be called out and studied in detail.
Scientists Detect Atomic Hydrogen In Most Distant Galaxy EverHubble Telescope Captures a Surreal Galaxy Merger Resulting in a ‘Colossal Ring’Scientists Discover Massive ‘Extra Galactic Structure’ Hidden Behind the Milky Way