Galaxies are not scattered randomly throughout the universe, but rather, along gigantic chains of hydrogen, galaxies are grouped into large groups of massive filaments, in what we know as the cosmic network, where galaxies are strung together which pearl necklace that surrounds the enormous voids of the cosmos. Each filament is basically a wall of galaxies, stretching for hundreds of millions of light years. They are the largest structures in the known universe.
Bringing together the cosmic web is one of the main assets of cosmology: having such a map would not only inform us about the structure of the universe and its interior, but could also help us better understand how the universe formed and how it evolved. over time.
Now, an international team of astronomers has discovered the presence of one of the largest cosmic structures discovered so far by man: a wall that stretches for 1.4 billion light years . Previously, other structures of this type, other larger “walls”, such as the Great Wall, the Sloan Great Wall, the Hercules-Corona Borealis Great Wall (spanning 9.7 billion light-years) and the Bootes Void had been identified.
But this one in particular is special. It’s very close! The South Pole wall, as it has been called, was hidden from the naked eye, remaining undetected until now because many parts of it lie just 500 million light-years away behind the bright Milky Way galaxy. In other words, our galaxy obstructs their vision. We haven’t found it so far for precisely that: it was hidden behind what astronomers sometimes call the Zone of Avoidance or Zone of Galactic Dimming: the galactic plane of the Milky Way.
How has it been discovered then?
Cosmological studies are usually carried out by measuring the redshift of objects – the speed at which those objects appear to be moving away from Earth due to the expansion of the universe. The faster an object moves back, the farther it is; that is, the farther away an object is, the faster it appears to be moving away from Earth, an observation first made by astronomer Edwin Hubble in 1929 and which has been maintained ever since.
The researchers made redshift observations as part of their study of the sky, but also added measurements of the velocity of certain galaxies, which illustrate how they gravitationally interact with each other. This technique can alert astronomers to invisible masses that, while typically used to investigate dark matter, it can also highlight masses obscured by bright light. Like in this case. Thus, with these data, scientists were able to map the South Pole Wall for the first time in history.
The resulting map shows an incredible blob of material roughly centered at the southernmost point in the sky, with a large sweeping wing extending north on one side in the direction of the constellation Cetus and another thicker arm opposite. in the direction of the constellation Apus.
Of course, “we will not be sure of its full scope, or if it is unusual, until we map the universe on a significantly larger scale ,” the authors point out.
Referencia: Daniel Pomarède et al. Cosmicflows-3: The South Pole Wall, The Astrophysical Journal (2020). DOI: 10.3847/1538-4357/ab9952
