Scientists create largest-ever cosmological simulation

A Chinese-led international team has released the largest-ever cosmological simulation, named "HyperMillennium," offering scientists a powerful digital tool to explore cosmic evolution.

This simulation covers a vast cube measuring 12 billion light-years per side and uses 4.2 trillion virtual dark matter particles. By applying a technique called N-body numerical simulation, the team accurately recreated the evolution of large-scale structures in the universe over 10 billion years. In simple terms, they built a virtual universe inside a supercomputer, starting just after the Big Bang and following gravity's pull step by step.

This virtual cosmos allows researchers to "rewind time" and study how galaxies and other cosmic features formed. By adding physical models of galaxy formation, the simulation produces a detailed catalog of galaxy positions, brightness and other key traits. This provides theoretical support for research into dark matter and dark energy, and also offers strong support for new-generation galaxy survey programs, such as the China Space Station Telescope and the European Space Agency's Euclid mission.

"The simulation was completed with high force resolution and time accuracy, and also made a breakthrough in computational scale. It allows scientists to study extremely rare, massive cosmic structures in fine detail while maintaining strong statistical power," said Wang Qiao, a researcher at the National Astronomical Observatories of the Chinese Academy of Sciences (NAOC).

Such large-scale simulations demand enormous computing resources, and the research team used self-developed software called PhotoNs, designed specifically for China's domestic supercomputers. After more than 10 years of work on algorithms and optimization, the team achieved efficient calculations using over 10,000 accelerator cards. The project consumed more than 100 million CPU core-hours and 10 million accelerator-card hours, and produced approximately 13 petabytes of raw and processed data.

Mike Boylan-Kolchin, a professor of the University of Texas at Austin, called the simulation a computational marvel that will help unlock secrets of dark energy and the early universe. He also noted that its unprecedented size and resolution make it a touchstone for research communities for years to come.

Volker Springel, the director of the Max Planck Institute for Astrophysics in Germany, said the simulation redefines the limits of numerical cosmology. He was "extremely impressed" by the team's effort in developing such an incredibly large and highly accurate simulation, which enables new high-precision tests of the standard cosmological model.

The first research paper stemming from this project was recently published in the journal Monthly Notices of the Royal Astronomical Society. As a demonstration of the power of the simulation, the team compared simulation results with real observations of Abell 2744, a famous galaxy cluster about four billion light-years from Earth. The match was remarkable, down to the pixel level, confirming that the standard cosmological model works even in extremely complex environments like colliding galaxy clusters.

According to the NAOC, the first batch of simulation data has already been released to the global scientific community through the National Astronomical Data Center, a platform for astronomy research, education and data-driven applications.