Counter to what most people may believe, galaxies are not evenly distributed in the universe and there are large areas of near emptiness. Most exist in groups and clusters which form large-scale structures, including gas filaments containing millions of galaxies.
These sheets and filaments tend to be separated by large voids where only a few galaxies are found.
Longest Gas Filament
Clusters of galaxies are bound by long cosmic threads of hot gas referred to as intergalactic filaments. Towards the end of 2020, a team scientist led by the University of Bonn managed to locate the longest ever filament, measuring an enormous 50 million light-years in length
This intergalactic filament structure matched computer simulations and predictions, providing insight into the origin and evolution of the universe.
Intergalactic filaments give rise to a cosmic web covering the observable universe. Galaxies are arranged within their structures in web-like patterns connected and surrounded by these filaments.
However, only around 5-percent of the universe is made up of visible matter, it is believed we can find half of the missing matter in elusive intergalactic gas filaments.
The Big Bang Theory
Scientists and astronomers believe that the Big Bang theory gave rise to our universe around 13.8 billion years ago. It was initially concentrated on one point but later expanded rapidly to form the universe.
The resultant effect was the ununiform spread out of cosmic matter. A good example is hydrogen gas, which was a bit denser in other parts hosting more gravitational forces drawing gas from their surroundings.
More matter concentrated in such regions over time separated by more generous expanses of voidness. After that, a sponge structure developed holes without any matter over the course of 13 billion years with areas in between housing the galaxy clusters.
Going by this reasoning, the galaxies and clusters should still be connected by thin spider web-like gas filaments. Researchers suggest that more than half of all baryonic matter in the universe lies in these filaments since many of them have been overstretched to the point that they are exceptionally diffuse.
It is believed that the matter in them has ten particles per cubic meter, lesser than the best vacuum that can exist on earth. Given their diffuse nature, it is almost impossible to spot these components through traditional methods.
Finding intergalactic gas filaments
Researchers came up with the e-rosita space telescope used in finding intergalactic gas filaments. This is an x-ray telescope built for extraterrestrial physics in Germany. University of Bonn researchers used it in finding the longest intergalactic filament, making it completely visible.
It has very sensitive detectors which makes it suitable for its purpose. It also has a wide field of view, capturing a large part of the sky in just one measurement. Through this, scientists discovered that the newly found longest intergalactic filament linked the three galactic structures that formed the superstructures of different bells, each located several million light-years in length.
Researchers suspect that they only saw part of this filament since galactic filaments are some of the longest known structures in the entire universe and are hard to detect.
Intergalactic webs can reveal a lot about the present-day universe and the processes that caused them.
The intergalactic medium is made up of ionized hydrogen. It also contains carbon-oxygen and small amounts of silicon. The elements do not glow significantly, and therefore are not observable to the human eye.
When light from distant galaxies travels through this medium, some of it is absorbed by the intergalactic gases, this is observable on a bar-graph as black lines when examined with a spectra analysis.