Year: 2025
Type: article
Abstract: 3I/ATLAS, the third discovered interstellar object, has a heliocentric speed of 58 km s −1 and exhibits cometary activity. To constrain the origin of 3I/ATLAS and its past dynamical evolution, we propagate the orbits of 3I/ATLAS and nearby stars to search for stellar encounters. Integrating orbits in the Galactic potential and propagating the astrometric and radial-velocity uncertainties of 30 million Gaia stars, we identify 25 encounters with median encounter distances less than 1 pc. However, because the encounter speeds between 3I/ATLAS and each encounter exceed 20 km s −1 , none is a plausible host under common ejection mechanisms. We infer stellar masses for most stars and quantify the gravitational perturbations exerted by each individual star or each binary system on 3I/ATLAS. The strongest gravitational scattering perturber is a wide M dwarf binary. Among all past encounters, the binary’s barycenter and 3I/ATLAS reach the small encounter distance of 0.24 2 − 0.084 + 0.089 pc and the encounter speed of 28.3 9 − 0.67 + 0.67 km s −1 1.64 Myr ago. We further demonstrate that the cumulative influence of the stellar encounters on both the speed and direction of 3I/ATLAS is weak. Based on the present kinematics of 3I/ATLAS to assess its origin, we find that a thin-disk origin is strongly favored because the thin disk both exhibits a velocity distribution closely matching that of 3I/ATLAS and provides the dominant local number density of stars.
Source: The Astronomical Journal
Authors: Yiyang Guo, Luyao Zhang, Fabo Feng, Zhao-Yu Li, Anton Pomazan, Xiaohu Yang
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $4,499
Funders: Natural Science Foundation of Shanghai, Chinese Academy of Sciences South America Center for Astronomy, European Space Agency, University of Leicester, University of Warwick, National Natural Science Foundation of China, China Scholarship Council, Shanghai Jiao Tong University, Higher Education Discipline Innovation Project, Office of Science, Fundamental Research Funds for the Central Universities, National Astronomical Observatories, Chinese Academy of Sciences
OpenAlex ID: W4416837396