What is the universe made of? Scientists have been searching for answers for thousands of years. We are familiar with planets, stars, galaxies and so on. After all, we live in the “ordinary” galaxy. However, there are many rare and amazing structures in the universe, such as a 1.4 billion light-year-long “wall”.
recently, an international research group led by Daniel pomared of the University of Sacre in Paris, France, has discovered one of the largest cosmic structures so far, the Antarctic wall, using the three-dimensional map of the universe. The wall, which contains hundreds of thousands of galaxies, is comparable in size to the Sloan wall, the sixth largest structure in the universe.
“the large-scale structure of the universe, similar to the ‘Antarctic wall’, is some of the denser regions in the universe.” Chen Xuelei, a researcher at the National Astronomical Observatory of the Chinese Academy of Sciences, said that the density of galaxies in these regions is higher than that in other regions, and there are filamentous structures. These massive structures are much larger than the largest cluster structure we have observed so far. The “Antarctic wall” was found in the direction of the zenith of the southern sky. Just imagine what a spectacular sight it is to have a huge city wall standing in front of you for 1.4 billion light-years.
giant cosmic structures like the “Antarctic wall” are rare, but not unique. In 2003, Richard Goth of Princeton University and his colleagues discovered a huge filamentous structure called Sloan’s great wall, which is 1.37 billion light-years long, but it is not the largest structure in the universe. In 2013, when looking for gamma ray bursts, astronomers accidentally discovered a huge structure with a length of up to 10 billion light-years, equivalent to 20% of the currently observable radius of the universe. This is the largest cosmic structure ever discovered – the great wall of Wuxian North corona.
“according to the current observations, it is speculated that the distribution of the early universe was relatively uniform, but there were also some small inhomogeneities, which were called primary disturbances.” Chen Xuelei said that due to the universal gravitation, the region with higher density will generate strong gravity, which will attract the surrounding materials and further enhance the density of the region, thus aggravating the heterogeneity of the universe, and gradually forming galaxies and larger scale structures.
these large-scale structures are formed by mutual attraction and aggregation due to gravitational interaction, which enables them to overcome the expansion effect of the universe, thus forming a loose structural system. Due to its loose structure, there is obvious interaction between it and the surrounding materials. Scientists have found that some galaxies move away from the earth faster than expected, while others are much slower. Perhaps these “walls” in the universe are the “culprits” for this phenomenon.
“to study the large-scale structure of the universe, we must first draw a three-dimensional map of the universe through sky surveys, including the use of optical and radio observations to obtain data on the large-scale structure of the universe.” Chen Xuelei explained.
However, the discovery of the “Antarctic wall” is very special. It is too close to us: only 500 million light-years away. It is almost as long as the Sloan wall, but it has been ignored because it is located in the dark area directly behind the Milky way and is obscured by the bright light from the galaxy. Researchers have found clues to the existence of other galaxies by observing their redshifts and velocities. Daniel pomared said the method allowed them to detect hidden masses that affect the motion of galaxies.
modern cosmology shows that the universe is dominated by dark matter and dark energy, but we still have no idea what dark matter is. However, a large amount of dark matter is likely to be hidden in large-scale structures such as the “Antarctic wall”.
the large-scale structure of the universe is an important probe to study the evolution history of the universe, including the formation process of the structure dominated by dark matter and the expansion of the universe caused by dark energy. “Although we can’t see dark matter directly, in the large-scale structure of the universe, dark matter is directly proportional to luminous matter, so in theory, dark matter should also be highly dense.” Chen Xuelei said.
obviously, the study of the “Antarctic wall” is not only related to the nearby galaxy, but also may be a guide for us to find dark matter. However, the researchers admit that they may not have drawn a complete “Antarctic wall” because it requires a map of the universe on a larger scale.