What lies between the great accumulations of matter in the universe? Astrophysicists have now been able to clarify that gigantic threads of gas run through the room. They discovered a 50 million light year long web that connects a system of three galaxy clusters. The researchers’ observations and model simulations confirm their ideas about the large-scale developments after the Big Bang.
It all began with a tremendous bang 13.8 billion years ago: According to the popular theory of the origin of the universe, the Big Bang was the beginning of space and time and gave birth to the structures that make up our universe. The whole matter was therefore concentrated on one point at the beginning and then expanded at breakneck speed. According to the models, a gigantic gas cloud was created in which the material was still relatively evenly distributed. But there were also decisive irregularities – with far-reaching consequences: In some places the cloud was a little denser after the Big Bang than in others and so these areas with increased gravitational force increasingly attracted matter and the surrounding space emptied.
On the trail of cosmic “cobwebs”
According to this formation model, the universe formed a kind of sponge structure within about 13 billion years: Large “holes” were created, in between areas in which thousands of galaxies romped in a small space – so-called galaxy clusters or clusters in which the stars are together Planets are located. But it is assumed that the intergalactic space was not completely emptied in the process. According to the assumptions, the galaxies and clusters are still connected by remnants of the original distribution of matter – like wafer-thin threads of a spider’s web.
The bottom line is that this residual matter is probably gigantic: “According to calculations, these filaments contain more than half of the total baryonic matter in our universe – that is the form of matter that stars and planets are made of, just like we ourselves,” explains Thomas Reiprich from der University of Bonn. But due to the enormous expansion of these structures, the matter in the filaments is extremely thinned: It is assumed that they contain just ten particles per cubic meter – that is much less than the best vacuum that can be created on earth. This is why the intergalactic webs have largely eluded astronomers.
A length of 50 million light years
But Reiprich and his international colleagues have now succeeded for the first time in making the gas comprehensively visible. The celestial object called Abell 3391/95 was in her sights. This is a system of three galaxy clusters that is around 700 million light years away from us. The astronomers focused the eROSITA space telescope on Abell 3391/95. “It has extremely sensitive detectors for the type of X-ray radiation emitted by the gas in the filaments,” explains Reiprich. “In addition, it has a large field of view – like a wide-angle lens, it depicts a relatively large part of the sky in a single measurement, and that in a very high resolution.” As he and his colleagues report, the space telescope made it possible in a comparative way to make detailed recordings of the extremely spacious structures in a short time.
As they report, in the eROSITA images, in addition to the clusters and the numerous individual galaxies of the system, the gas threads that connect these structures with each other were now also visible. The entire filament system in view was 50 million light years long, according to the scientists’ calculations. But it may be even bigger: Reiprich and his colleagues assume that the previous images only show a section of the entire filament complex of Abell 3391/95.
As part of their study, the astronomers also compared their observations with the results of a simulation that simulates the evolution of the universe. As they report, the results show that the theoretical assumptions match reality: “The eROSITA images are strikingly similar to the computer-generated graphics. This suggests that the widely accepted standard model for the development of the universe is correct, ”says Reiprich.
Thus, the results of the study confirm the previous assumptions about where the enormous amounts of baryonic matter in the universe are hidden, which have so far remained invisible: in the unimaginably large, filamentous structures made of gas that surround and connect galaxies and galaxy clusters.
Source: University of Bonn, specialist article: Astronomy & Astrophysics, doi: 10.1051 / 0004-6361 / 202039590