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Jean-Eudes Arlot (LTE), Valéry Lainey (LTE)08/04/2026 10:50
Les satellites galiléens constituent probablement le système satellitaire le plus étudié du système solaire. Leur dynamique est la plus complexe, mais aussi la plus intéressante. Aujourd'hui, son étude devient un moyen d’exploration et de compréhension de l’origine de ce système de satellites. Nous aborderons cette longue histoire, en particulier au Bureau des longitudes (qui deviendra l’IMCCE...
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Ettore Perozzi08/04/2026 11:50
Back in 2007 I was appointed Scientific Director of the Space Academy Foundation, jointly promoted by Telespazio, Thales Alenia Space Italia and The University of L’Aquila to foster high level training on space-related issues. To this end the workshop ”Novel Spaceways for Scientific and Exploration Missions” was organized at the Telespazio Fucino Space Center. The aim was to investigate the...
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Alain Albouy (LTE)08/04/2026 14:00
Gauss explained in 1818 that the attraction of a body A by another body B moving on a Keplerian orbit is after averaging the attraction of A by a 1-dimensional ring with the shape of the Keplerian ellipse and a mass distribution $dm$ proportional to $dl$ where $l$ is the mean anomaly (and of total mass the mass of B).
Gauss did not invent this averaging but rather invented the 1-dimensional...
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Ziyu Liu (LTE)08/04/2026 14:00
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Raphaël Lallemand (LTE)08/04/2026 14:00
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Alexandre Bougakov (LTE)08/04/2026 14:00
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Alessia Francesca Guido08/04/2026 14:00
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Gwenaël Boué (LTE)08/04/2026 14:00
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Alexandre Prieur (LTE)08/04/2026 14:00
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Baptiste Loire (LTE)08/04/2026 14:00
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Mickaël Gastineau (LTE)08/04/2026 14:00
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Baptiste Loire (LTE)08/04/2026 14:00
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Sylvio Ferraz-Mello09/04/2026 10:30
The potentially habitable zone (PHZ) of solar-type stars is not very close to the stars and the tidal effects on the planets are not so large on planets in compact systems.
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Circularization and synchronization are not so fast and the 1:1 spin-orbit resonance is no longer a necessary fate.
Two important examples are Mercury and Venus in our Solar System.
Tidal theories show that, for orbits... -
Alexandre Correia09/04/2026 11:10
We present new methods for modeling the tidal evolution of multi-body systems. We derive the equations of motion using a vectorial formalism that is frame-independent and applicable to any rheological model. We compute the instantaneous deformation of extended bodies by solving a differential equation for the inertia tensor. This approach can account for all types of perturbations, including...
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Alessandra Celletti09/04/2026 11:50
We present results on the computation of proper elements for space debris around the Earth; they are obtained through suitable computations of normal forms.
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We show that perturbative methods can be integrated with Machine Learning techniques, specifically to investigate the dynamics of groups of objects for the classification and clustering of space debris generated by break-up events of... -
Gwenaël Boué (LTE)09/04/2026 14:30
The modeling of solid tides plays a central role in understanding the long-term dynamical evolution of planetary and satellite systems. In this presentation, we review the development of tidal models in celestial mechanics, tracing the progression from the simple constant time-delay prescription to more physically grounded approaches based on rheological properties of planetary bodies. Special...
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Valentin Etienne (LTE)09/04/2026 15:10
Analytical models describing the rotation of celestial bodies with a viscous fluid core commonly assume a simple motion for the fluid - a solution originally derived by Hough and Poincaré for a perfect (inviscid) fluid. In these models, viscosity is subsequently introduced ad hoc through an empirical friction torque at the core-mantle interface.
We propose a new analytical model in which...
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Pierre Auclair-Desrotour (LTE)09/04/2026 16:10
Oceanic and thermal tides exert a profound influence on the long-term rotational evolution of rocky planets. Oceanic tides arise from gravitational tidal forces, whereas thermal tides originate from diurnal contrasts in stellar irradiation. Both types of tide exhibit resonant behaviour, enabling substantial amplification of the induced tidal torques. Notably, tidal resonances have shaped the...
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Baptiste Loire (LTE)09/04/2026 16:50
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Jacques Laskar (LTE)10/04/2026 10:30
Due to tidal interaction between the Earth and the Moon, dissipation occurs, slowing Earth's rotation while causing the Moon to move away from the Earth at a present rate of 3.8 cm per year. Laser reflectors left by Apollo astronauts on the Moon's surface enable extremely precise measurements of this recession. Meanwhile, rock samples brought back from the same Apollo missions helped estimate...
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Alessandro Morbidelli10/04/2026 11:10
The last giant impact on Earth is thought to have formed the Moon. The timing of this event can be determined by dating the different rocks assumed to have crystallized from the lunar magma ocean (LMO). This has led to a wide range of estimates for the age of the Moon between 4.35 and 4.51 billion years ago (Ga), depending on whether ages for lunar whole-rock samples or individual zircon...
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Nicolas Rambaux (LTE)10/04/2026 11:50
Lunar rotation can be measured with high precision using lunar laser ranging observations collected over the past five decades. The long time span of these data, combined with centimeter-level accuracy, enables the identification and characterization of geophysical mechanisms affecting the Moon's rotation such as tidal contribution and signatures of interior structure. These small effects are...
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Bruno Sicardy (LTE)10/04/2026 14:30
Rings are made up of countless test particles that can be perturbed by satellites with circular or elliptic orbits. At first sight, resonances effects on the disk can be satisfactorily described in the context of the Planar Restricted Three-Body Problem (PR3BP). However, an essential ingredient is missing in the PR3BP approach: the interactions between particles, either by local inelastic...
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Jérémy Couturier10/04/2026 15:10
While two-planet mean-motion resonances have been extensively studied, the dynamics of three-planet resonances are comparatively less understood, especially when tidal dissipation is involved. We present a one-parameter one-degree-of-freedom pendulum-like model of three-planet zeroth-order resonances of the form $pn_1 − (p + q) n_2 + qn_3 = 0$ based on a Hamiltonian expansion carried out to...
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Rudolf Dvorak10/04/2026 16:10
In the Jupiter system with its numerous moons there are four of them even visible without a telescope.
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The three innermost ones namely Io (P=1.77d) Europa (P=3.55d) and Ganymede (P=7.15) are caught in a special 1:2:4 Mean Motion Resonance! This so called Laplace Resonance was and is a permanent topic for research in Celestial Mechanics. In our study we tackle the problem from the analytical... -
Zoran Knežević10/04/2026 16:50
The asteroid proper element catalogs nowadays typically contain data
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sets for more than a million asteroids, and are available from
different sources. The computation of proper elements fails in some
cases due to various dynamical or computational causes, e.g.
resonances or close approaches to perturbing planets. We assess the
significance of these cases in the overall proper elements...
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