Galaxy Filaments

When we look at a map of the galaxies, we can find that they are not randomly distributed across the universe. Instead, they form in large clusters, which are part of even larger superclusters, of which they are around 10 million. Nevertheless, due to careful analysis of mass distribution in galaxies, astrophysicists have determined that there are dark matter filaments that hold these clusters together. They are some of the largest structures out there. Let’s explore how they form and some of their properties.

A visualisation of a galactic filament. Credit: Rich Murray.

The filaments are said to have formed in the Big Bang, due to primordial density fluctuations due to fluctuations in the quantum field. What that means is that small differences in mass distribution a few microseconds after the formation of the universe, created these large superstructures over time through expansion. It’s kind of like the butterfly effect from chaos theory, where small changes in initial conditions result in huge implications after a while.

Structures larger than superclusters begun getting discovered in the 1980s. R. Brent Tully, working at the University of Hawaii Institute of Astronomy discovered the Pisces–Cetus Supercluster Complex, which houses 60 smaller clusters. Subsequent discoveries distinguished two types of filaments, flat horizontal ones and thin vertical ones. The latter are called galaxy walls and we have discovered a larger amount of them. One such wall, the Hercules–Corona Borealis Great Wall, is a largest structure in the observable universe. It was discovered in 2012 and named by a Filipino teenager on Wikipedia! It is so massive that there have been numerous papers that attempted to disprove it, nevertheless the authors keep successfully responding to the doubters.

A map of the nearest galaxy walls. Credit: Richard Powell.

Recently, it was discovered by a team of scientists working on a 3D model of galaxy filaments using data from the Sloan Digital Sky survey, that these superstructures spin. This is interesting, as the current model of the formation of the universe suggests that matter flowed from dense to less dense regions, however with no torque associated with it. Therefore, a spin on such a large scale means that something might be wrong with our idea of the Big Bang, as these structures had to get the angular momentum from somewhere. The authors make it clear that not all filaments spin, however thinking about the universe as a collection of spinning clusters definitely plays with the mind.

It is interesting to imagine our universe as having a hidden system of connections made of dark matter. I have always viewed it as a ballon or a void that just houses little randomly distributed specks of galaxies and stars. Nevertheless, it seems like there is a lot more than meets the eye. Recent research showed that quasars are a possible way of “illuminating” these dark matter filaments, therefore with better equipment we might be able to deduce an even bigger structure. Who knows, perhaps everything is connected with one giant filament?


Galactic Filaments | COSMOS. (n.d.). Cosmos.

Redfern, S. (2014, January 23). Filaments that bind galaxies together illuminated by a quasar. The Conversation.

Wikipedia contributors. (2021a). Galaxy filament. Wikipedia.

Wikipedia contributors. (2021b). Hercules–Corona Borealis Great Wall. Wikipedia.

(2021, June 22). The Largest Rotating Objects in the Universe: Galactic Filaments Hundreds of Millions of Light-Years Long. Universe Today.

Published by Mateusz Ratman

High school student from Warsaw, Poland. JHU Class of 2026.

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