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3I/ATLAS: In Search of the Witnesses to Its Voyage

Pérez-Couto, X. ; Torres, S. ; Villaver, E. ; Mustill, A.~J. LU orcid and Manteiga, M. (2026) In Astrophysical Journal 1001(2).
Abstract
3I/ATLAS is the third interstellar object discovered to date, following 1I/‘Oumuamua and 2I/Borisov. Its unusually high excess velocity and active cometary nature make it a key probe of the Galactic population of icy planetesimals. Understanding its origin requires its past trajectory through the Galaxy to be traced and the possible role of stellar encounters to be assessed, both as a potential origin and a perturber to its orbit. We integrated the orbit of 3I/ATLAS backward in time for 10 Myr, together with a sample of Gaia DR3 stars with high-quality astrometry and radial velocities, to identify close passages within 2 pc. We identify 93 nominal encounters, 62 of which are significant at the 2σ level. However, none of these encounters... (More)
3I/ATLAS is the third interstellar object discovered to date, following 1I/‘Oumuamua and 2I/Borisov. Its unusually high excess velocity and active cometary nature make it a key probe of the Galactic population of icy planetesimals. Understanding its origin requires its past trajectory through the Galaxy to be traced and the possible role of stellar encounters to be assessed, both as a potential origin and a perturber to its orbit. We integrated the orbit of 3I/ATLAS backward in time for 10 Myr, together with a sample of Gaia DR3 stars with high-quality astrometry and radial velocities, to identify close passages within 2 pc. We identify 93 nominal encounters, 62 of which are significant at the 2σ level. However, none of these encounters produced any meaningful perturbation. The strongest perturber Gaia DR3 6863591389529611264 at 0.30 pc and with a relative velocity of 35 km s−1, imparted only a velocity change of ∣Δv∣ ≃ 5 × 10−4 km s−1 to the orbit of 3I/ATLAS. Our results indicate that no stellar flybys within the past 10 Myr and 500 pc contained in Gaia DR3 can account for the present trajectory of 3I/ATLAS or be associated with its origin. We further show that 3I/ATLAS is kinematically consistent with a thin-disk population, despite its large peculiar velocity. © 2026. The Author(s). Published by the American Astronomical Society. (Less)
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author
; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Interstellar objects, Gaia, Milky Way dynamics, Astrometry, Close encounters, 52, 2360, 1051, 80, 255, Earth and Planetary Astrophysics, Astrophysics of Galaxies
in
Astrophysical Journal
volume
1001
issue
2
article number
146
publisher
American Astronomical Society
external identifiers
  • scopus:105035882647
ISSN
0004-637X
DOI
10.3847/1538-4357/ae56ff
language
English
LU publication?
yes
id
6df4018e-c7ad-4e55-9cb5-c3616091ff81
date added to LUP
2026-05-11 15:39:16
date last changed
2026-05-12 08:26:34
@article{6df4018e-c7ad-4e55-9cb5-c3616091ff81,
  abstract     = {{3I/ATLAS is the third interstellar object discovered to date, following 1I/‘Oumuamua and 2I/Borisov. Its unusually high excess velocity and active cometary nature make it a key probe of the Galactic population of icy planetesimals. Understanding its origin requires its past trajectory through the Galaxy to be traced and the possible role of stellar encounters to be assessed, both as a potential origin and a perturber to its orbit. We integrated the orbit of 3I/ATLAS backward in time for 10 Myr, together with a sample of Gaia DR3 stars with high-quality astrometry and radial velocities, to identify close passages within 2 pc. We identify 93 nominal encounters, 62 of which are significant at the 2σ level. However, none of these encounters produced any meaningful perturbation. The strongest perturber Gaia DR3 6863591389529611264 at 0.30 pc and with a relative velocity of 35 km s−1, imparted only a velocity change of ∣Δv∣ ≃ 5 × 10−4 km s−1 to the orbit of 3I/ATLAS. Our results indicate that no stellar flybys within the past 10 Myr and 500 pc contained in Gaia DR3 can account for the present trajectory of 3I/ATLAS or be associated with its origin. We further show that 3I/ATLAS is kinematically consistent with a thin-disk population, despite its large peculiar velocity. © 2026. The Author(s). Published by the American Astronomical Society.}},
  author       = {{Pérez-Couto, X. and Torres, S. and Villaver, E. and Mustill, A.~J. and Manteiga, M.}},
  issn         = {{0004-637X}},
  keywords     = {{Interstellar objects; Gaia; Milky Way dynamics; Astrometry; Close encounters; 52; 2360; 1051; 80; 255; Earth and Planetary Astrophysics; Astrophysics of Galaxies}},
  language     = {{eng}},
  month        = {{04}},
  number       = {{2}},
  publisher    = {{American Astronomical Society}},
  series       = {{Astrophysical Journal}},
  title        = {{3I/ATLAS: In Search of the Witnesses to Its Voyage}},
  url          = {{http://dx.doi.org/10.3847/1538-4357/ae56ff}},
  doi          = {{10.3847/1538-4357/ae56ff}},
  volume       = {{1001}},
  year         = {{2026}},
}