arXiv subjects

Alessandra Ferreira

Publications and source records attributed to Alessandra Ferreira.

2 recordsLinked to original sources

arXiv2026

Equilibrium Points and Surface Dynamics About Comet 67P/Churyumov-Gerasimenko

Small bodies in our Solar System are considered remnants of their early formation. Studying their physical and dynamic properties can provide insights into their evolution, stability, and origin. ESA's Rosetta mission successfully landed and studied comet Churyumov-Gerasimenko (67P) for approximately two years. In this work, the aim is to analyze the surface and orbital dynamics of comet 67P in detail, using a suitable 3-D polyhedral shape model. We applied the polyhedron method to calculate dynamic surface characteristics, including geometric height, surface tilt, surface slopes, geopotential surface, acceleration surface, escape speed, equilibrium points, and zero-velocity curves. The results show that the gravitational potential is predominant on the comet's surface due to its slow rotation. The escape speed has the maximum value in the Hapi region (the comet's neck). The surface slopes were analyzed to predict possible regions of particle motion and accumulation. The results show that most regions of the comet's surface have low slopes. Furthermore, we analyzed the slopes under the effects of Third-Body gravitational and Solar Radiation Pressure perturbations. Our results showed that the effects of Third-Body perturbations do not significantly affect the global behavior of slopes. Meanwhile, the Solar Radiation Pressure does not significantly affect particles across the surface of comet 67P with sizes $>\sim10^{-3}$\,cm at apocenter and $>\sim10^{-1}$\,cm at pericenter. We also identified four equilibrium points around comet 67P and one equilibrium point inside the body, where points E$_2$ and E$_5$ are linearly stable. In addition, we approximated the shape of comet 67P using the simplified Dipole Segment Model to study its dynamics, employing parameters derived from its 3-D polyhedral shape model. We found 12 families of planar symmetric periodic orbits around the body.

astro-ph.EP↗

arXiv2026

Surface Properties, Orbital Dynamics, and Thermophysical Modeling of the Primitive Asteroid (269) Justitia

The Emirates Mission to the Asteroid Belt (EMA) will study the ultra-red asteroid (269)~Justitia. In this work, we present the first detailed investigation of Justitia's surface dynamics using the newly developed 3-D polyhedral shape model with 574 vertices and 1,144 faces. We analyze its geopotential, surface acceleration, escape speeds, slopes, and equilibrium points, and we also search for planar symmetric periodic orbits using an equivalent ellipsoidal approximation. Our results indicate that the lowest geopotential values occur at the poles, which also correspond to regions of maximum surface acceleration. The global slope distribution suggests preferred zones of material accumulation or migration, offering clues to Justitia's long-term morphological evolution. Most slopes remain below $40^\circ$, implying that loose particles may settle stably across large portions of the surface. We identify five equilibrium points consistent with Justitia's estimated density and slow rotational period. Two external points (E$_2$ and E$_4$) exhibit linear stability, and all equilibrium locations lie relatively far from the surface due to the body's slow spin. Additionally, we discover 28 new families of planar symmetric periodic orbits, then classify their topologies and determine their linear stability, providing a dynamical framework relevant to future spacecraft operations near Justitia. Finally, thermal modeling reveals how thermal inertia and heliocentric distance shape Justitia's temperature distribution. The south pole receives more insolation than the north pole, reaching minimum temperatures of about 102~K and 87~K, respectively. These combined dynamical and thermal results offer valuable insights for the EMA mission and for understanding slowly rotating small bodies.

astro-ph.EP↗