Elucidate the large-scale structure of the universe with the world’s largest international groups, such as Chiba University.

An international research group led by Chiba University has announced that it has completed the world’s largest “simulated universe” that simulates the structure of the universe. As a result of the full use of the supercomputer (supercomputer) of the National Astronomical Observatory of Japan, this simulated universe made up of a large amount of data received the name “Uchuu (universe)”. The research group compresses the data significantly and publishes it in a user-friendly format. It is said to be useful for the detailed elucidation of the large-scale structure of the universe and the formation of galaxies, which are surrounded by many mysteries.

In the universe, there are substances called dark matter that are invisible and cannot be observed by light or radio waves, unlike substances that are directly visible to the eye (baryons), which are estimated to be 5 to 6 times larger than baryons. in terms of mass. It is a mysterious substance that works only by gravity and occupies approximately 80% of the mass of the universe. Dark matter creates a huge lump-like structure called a “halo” due to its gravity, and the baryonic gas accumulated by the halo’s gravity contracts at the center to form stars and galaxies. It is believed that the structure of the current universe was created.

However, the detailed process of how galaxies and other celestial bodies in the halo were born and evolved to form the large-scale structure of the universe has become a great mystery of astronomy.

According to the research group, astronomical observations are continued daily with the “Subaru Telescope” operated by the National Astronomical Observatory of Japan on the summit of Mauna Kea in Hawaii, United States, in order to unravel the mystery. However, to extract information about the history of the formation of the structure of the universe from the results of the observation, it was necessary to compare it with the simulated universe created based on physical theory.

To create a simulated universe, it is necessary to use a computer to simulate the gravitational interaction of dark matter from the birth of the universe to the present. However, the computing capabilities used in previous studies have not reached the level of spatial size and precision necessary for comparison with observations.

Therefore, associate professor Tomoaki Ishiyama from the Chiba University Integrated Information Center of the research group decided to use the entire system of the “Aterui II” supercomputer of the Japan National Astronomical Observatory.

The research group made full use of the 40,200 CPU cores installed in Aterui II. Then, by expressing the dark matter particles with 2.1 trillion particles and calculating the gravity acting on them, we were able to draw in detail the structure of the simulated universe created by dark matter. “Uchuu” is 9.6 billion light years on a side. It is possible to follow the evolution of celestial bodies of various mass scales, from dwarf galaxies to giant galaxy clusters, which are less than one hundredth the size of the average galaxy.

Uchuu’s data totals 3,000 trillion bytes, but the research group has significantly compressed all of the data with high-performance computing technology. It was released on the Internet in a format that anyone can use as basic data of approximately 100 trillion bytes specialized in the formation of dark object structures.

Associate Professor Ishiyama said: “It is difficult to track the evolution of a celestial body by observation, but it is possible to follow the evolution in this simulation (simulated universe). It can be expected to contribute to the understanding of the formation process and evolution of existing galaxy clusters “.

In addition to Japan and Spain, the international research group includes researchers from nine countries, including the United States, Australia, Italy, France, Spain, Argentina, and Chile. The research results were published in the September issue of the British Journal of the Royal Astronomical Society.

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