4.6 billion years of solar system migration explored by short-lived radionuclides and galaxy simulations

2023 Fiscal Year Final Research Report

• Project/Area Number: 22K20387
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Multi-year Fund
• Review Section: 0204:Astronomy, earth and planetary science, and related fields
• Research Institution: The University of Aizu
• Principal Investigator: Fujimoto Yusuke 会津大学, コンピュータ理工学部, 准教授 (90965691)
• Project Period (FY): 2022-08-31 – 2024-03-31
• Keywords: 銀河系 / 太陽系 / 数値シミュレーション

Outline of Final Research Achievements

Stars in the Galactic disc, including the Solar system, have deviated from their birth orbits and have experienced radial mixing and vertical heating. By performing hydrodynamical simulations of a galactic disc, we investigate how much tracer particles, which are initially located in the disc to mimic newborn stars and the disc stars, are displaced from initial near-circular orbits by gravitational interactions with giant molecular clouds (GMCs). We investigate the time evolution of the radial and vertical velocity dispersion and find that they keep fast and efficient disc heating for 1 Gyr. We find that the efficient stellar scattering by GMCs also causes a change in angular momentum for each star and, therefore, radial migration of more than 1 kpc in the radial direction for 1 Gyr. This effect is more pronounced in newborn stars than old disc stars. The dynamical heating and radial migration drastically occur in the first several hundred Myr.

Free Research Field

天文学

Academic Significance and Societal Importance of the Research Achievements

太陽系が誕生した46億年前から現在に至るまで、銀河円盤内における太陽系やその他恒星の移動についての理解を目指す本研究は、隕石分析や小惑星探査機「はやぶさ２」などが持ち帰った小惑星資料の解析による太陽系形成研究と、ALMA電波望遠鏡やすばる望遠鏡などによる系外惑星研究を繋ぐ橋渡しの役割を担うという学術的意義を持つ。また、太陽系が天の川銀河のどこで生まれ、どのように彷徨い、今現在どのような所に存在し、そして今後どこに向かうのかを理解することは天文学や惑星科学の学術範囲を超え、広く人類にとっての社会的意義を持つ。