{"ID":2849633,"CreatedAt":"2026-06-01T04:54:23.091178241Z","UpdatedAt":"2026-06-01T04:54:23.091178241Z","DeletedAt":null,"paper_url":"https://arxiv.org/abs/2510.23330","arxiv_id":"2510.23330","title":"The First Star-by-star $N$-body/Hydrodynamics Simulation of Our Galaxy Coupling with a Surrogate Model","abstract":"A major goal of computational astrophysics is to simulate the Milky Way Galaxy with sufficient resolution down to individual stars. However, the scaling fails due to some small-scale, short-timescale phenomena, such as supernova explosions. We have developed a novel integration scheme of $N$-body/hydrodynamics simulations working with machine learning. This approach bypasses the short timesteps caused by supernova explosions using a surrogate model, thereby improving scalability. With this method, we reached 300 billion particles using 148,900 nodes, equivalent to 7,147,200 CPU cores, breaking through the billion-particle barrier currently faced by state-of-the-art simulations. This resolution allows us to perform the first star-by-star galaxy simulation, which resolves individual stars in the Milky Way Galaxy. The performance scales over $10^4$ CPU cores, an upper limit in the current state-of-the-art simulations using both A64FX and X86-64 processors and NVIDIA CUDA GPUs.","short_abstract":"A major goal of computational astrophysics is to simulate the Milky Way Galaxy with sufficient resolution down to individual stars. However, the scaling fails due to some small-scale, short-timescale phenomena, such as supernova explosions. We have developed a novel integration scheme of $N$-body/hydrodynamics simulati...","url_abs":"https://arxiv.org/abs/2510.23330","url_pdf":"https://arxiv.org/pdf/2510.23330v1","authors":"[\"Keiya Hirashima\",\"Michiko S. Fujii\",\"Takayuki R. Saitoh\",\"Naoto Harada\",\"Kentaro Nomura\",\"Kohji Yoshikawa\",\"Yutaka Hirai\",\"Tetsuro Asano\",\"Kana Moriwaki\",\"Masaki Iwasawa\",\"Takashi Okamoto\",\"Junichiro Makino\"]","published":"2025-10-27T13:45:55Z","proceeding":"astro-ph.GA","tasks":"[\"astro-ph.GA\",\"cs.DC\",\"cs.LG\",\"physics.comp-ph\"]","methods":"[]","has_code":false}