Galactic tides in the Solar System within a non-axisymmetric Milky Way model adjusted to Gaia data
Abstract
Context. Galactic tides are external differential forces acting on extended systems immersed in the Galactic potential. They play a key role in the dynamics of comets in the Oort cloud. Aims. We aim to establish the strength of Galactic tides from the non-axisymmetric potential of the Milky Way revealed by the Gaia mission, and how this strength evolves along the Galactic trajectory of the Solar System. Methods. We derived expressions for Galactic tide parameters independently of any simplified trajectory for a star in the Galaxy or any specific symmetry of the Galactic potential. We obtained six parameters, G1 to G6, that quantify the influence of tides. Using the most up-to-date Galactic potential model, extended here to three dimensions, we studied the time evolution of these parameters along the Sun's trajectory using a statistical approach. Results. Even for Galactic trajectories featuring modest radial and vertical excursions, as investigated here, the dominant Galactic parameter, G3, is found to vary by an order of magnitude along the solar trajectory. G1 and G2 reach up to about one half and one quarter, respectively, of G3 along the solar trajectory, whilst parameters G4 to G6 reach up to one tenth of G3. Conclusions. Contrary to what is often assumed, all Galactic tide parameters vary widely along the Galactic trajectory of the Solar System. Two consequences can be expected: First, G3 directly affects the flux of observable long-period comets and the extent of the fossilised Sednoids region; second, G1 and G2, and to a lesser extent, G4 to G6, break the integrability of the dynamics, potentially affecting the long-term structure of the Oort cloud. Additionally, the new parameters G4 to G6, while small for the Solar System, may strongly impact extrasolar systems with a large out-of-the-plane excursion in the Galaxy.
Versions
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BibTeX
@misc{bougakov2026galactic,
title = {{Galactic tides in the Solar System within a non-axisymmetric Milky Way model adjusted to Gaia data}},
author = {Alexandre Bougakov and Yassin Rany Khalil and Marc Fouchard and Melaine Saillenfest and Benoit Famaey and Paola Di Matteo and Misha Haywood},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.02693},
eprint = {2609.02693},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.02693},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Galactic tides in the Solar System within a non-axisymmetric Milky Way model adjusted to Gaia data
AU - Alexandre Bougakov
AU - Yassin Rany Khalil
AU - Marc Fouchard
AU - Melaine Saillenfest
AU - Benoit Famaey
AU - Paola Di Matteo
AU - Misha Haywood
PY - 2026
DA - 2026/09/02
PB - arXiv
DO - 10.48550/arxiv.2609.02693
UR - https://arxiv.org/abs/2609.02693
AB - Context. Galactic tides are external differential forces acting on extended systems immersed in the Galactic potential. They play a key role in the dynamics of comets in the Oort cloud. Aims. We aim to establish the strength of Galactic tides from the non-axisymmetric potential of the Milky Way revealed by the Gaia mission, and how this strength evolves along the Galactic trajectory of the Solar System. Methods. We derived expressions for Galactic tide parameters independently of any simplified trajectory for a star in the Galaxy or any specific symmetry of the Galactic potential. We obtained six parameters, G_1 to G_6, that quantify the influence of tides. Using the most up-to-date Galactic potential model, extended here to three dimensions, we studied the time evolution of these parameters along the Sun's trajectory using a statistical approach. Results. Even for Galactic trajectories featuring modest radial and vertical excursions, as investigated here, the dominant Galactic parameter, G_3, is found to vary by an order of magnitude along the solar trajectory. G_1 and G_2 reach up to about one half and one quarter, respectively, of G_3 along the solar trajectory, whilst parameters G_4 to G_6 reach up to one tenth of G_3. Conclusions. Contrary to what is often assumed, all Galactic tide parameters vary widely along the Galactic trajectory of the Solar System. Two consequences can be expected: First, G_3 directly affects the flux of observable long-period comets and the extent of the fossilised Sednoids region; second, G_1 and G_2, and to a lesser extent, G_4 to G_6, break the integrability of the dynamics, potentially affecting the long-term structure of the Oort cloud. Additionally, the new parameters G_4 to G_6, while small for the Solar System, may strongly impact extrasolar systems with a large out-of-the-plane excursion in the Galaxy.
ER -