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A cosmic web of infinite length discovered by astronomers
A cosmic web of infinite length discovered by astronomers

Observations of one of the largest clusters of galaxies in the constellation of Aquarius helped astronomers to obtain the first detailed photographs of the strands of the "cosmic web" that connects all the clusters of matter in the universe. The pictures were published by the scientific journal Science.

“In the past, we have already been able to see the glow produced by these gas bubbles located outside galaxies. astrophysicist Hideki Umehata of the RIKEN Research Center in Saitama, Japan.

Cosmologists suggest that the structure of the universe is similar to an endless three-dimensional web, whose threads are almost entirely composed of large clusters of dark matter. At the points of intersection of these filaments, there are dense lumps of visible matter, including individual galaxies and groups of "star megacities".

Astronomers study the properties and nature of this web by observing distant galaxies and fluctuations in the brightness of the so-called relic radiation, which is a kind of "echo" of the Big Bang. It preserved information about how dark matter was distributed throughout the Universe and made it extremely heterogeneous in composition and density.

By themselves, the strands of the "cosmic web", as noted by Umehata and his colleagues, astronomers have not yet directly seen. First of all, this is hindered by the fact that the bright light of galaxies and their clusters overshadows the extremely weak glow of its filaments in the infrared range. Only in some fortunate cases, when the "germ" of the galaxy arose inside them, astronomers could see some of this gas.

These modest successes have prevented cosmologists from understanding if one of the biggest problems in modern science exists - why the universe supposedly contains half the amount of matter that theory predicts. Filaments, threads of the "cosmic web", can harbor this "missing" matter, which would explain the discrepancies and save the theory from revision.

Mysteries of the space "forest"

Umehata and his colleagues have taken a big step towards answering this question. They observed the glow that hydrogen atoms living inside the "cosmic web" produce when interacting with the so-called Lyman forest, the ultraviolet background radiation of the universe.

As a rule, its brightness is relatively low, but the largest and brightest galaxies that existed in the first epochs of the life of the universe, produced a lot of such particles of light. Accordingly, if the threads of the "web" are located near such galaxies, then they will glow brightly enough in that part of the spectrum that is associated with the Lyman "forest".

Guided by this idea, Japanese and European astronomers observed the emerging cluster of galaxies SSA22, the light from which travels to Earth for about 12 billion years. Thanks to such a large distance, we see it in the state in which it existed in the first 2 billion years of the life of the Universe.

To search for traces of the "cosmic web" filaments, scientists used the European VLT telescope, one of the largest ground-based optical observatories, as well as the MUSE spectroscope, which can very effectively "remove" the glow of galaxies themselves and other inhabitants of space from the picture.

By comparing the VLT images with the photographs of the same galaxy cluster that other observatories received, scientists were able to see for the first time the full-fledged filaments of the "cosmic web".They do connect many of the ancient galaxies that are forming and spanning many millions of light years.

In general, their photographs confirmed the current ideas about how the Universe works - the galaxies were indeed located at those points where the threads of the "web" intersected, which fully corresponds to the predictions of modern cosmology. Scientists hope that further observations of SSA22 will help them calculate the mass of gas in these filaments and begin a serious search for the "missing" matter of the universe.

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