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Register a new userAsteroid secular dynamics: Ceres fingerprint identified
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Here we report on the significant role of a so far overlooked dynamical aspect, namely a secular resonance between the dwarf planet Ceres and other asteroids. We demonstrate that this type of secular resonance can be the dominant dynamical factor in certain regions of the main asteroid belt. Specifically, we performed a dynamical analysis of the asteroids belonging to the (1726) Hoffmeister family. To identify which dynamical mechanisms are actually at work in this part of the main asteroid belt, i.e. to isolate the main perturber(s), we study the evolution of this family in time. The study is accomplished using numerical integrations of test particles performed within different dynamical models. The obtained results reveal that the post-impact evolution of the Hoffmeister asteroid family is a direct consequence of the nodal secular resonance with Ceres. This leads us to the conclusion that similar effects must exist in other parts of the asteroid belt. In this respect, the obtained results shed light on an important and entirely new aspect of the long-term dynamics of small bodies. Ceres fingerprint in asteroid dynamics, expressed through the discovered secular resonance effect, completely changes our understanding of the way in which perturbations by Ceres-like objects affect the orbits of nearby bodies.
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We consider the role of the dwarf planet Ceres on the secular dynamics of the asteroid main belt. Specifically, we examine the post impact evolution of asteroid families due to the interaction of their members with the linear nodal secular resonance with Ceres. First, we find the location of this resonance and identify which asteroid families are crossed by its path. Next, we summarize our results for three asteroid families, namely (1726) Hoffmeister, (1128) Astrid and (1521) Seinajoki which have irregular distributions of their members in the proper elements space, indicative of the effect of the resonance. We confirm this by performing a set of numerical simulations, showcasing that the perturbing action of Ceres through its linear nodal secular resonance is essential to reproduce the actual shape of the families.
Close-in planets evolve under extreme conditions, raising questions about their origins and current nature. Two predominant mechanisms are orbital migration, which brings them close to their star, and atmospheric escape under the resulting increased irradiation. Yet, their relative roles remain unclear because we lack models that couple the two mechanisms with high precision on secular timescales. To address this need, we developed the JADE code, which simulates the secular atmospheric and dynamical evolution of a planet around its star, and can include the perturbation induced by a distant third body. On the dynamical side, the 3D evolution of the orbit is modeled under stellar and planetary tidal forces, a relativistic correction, and the action of the distant perturber. On the atmospheric side, the vertical structure of the atmosphere is integrated over time based on its thermodynamical properties, inner heating, and the evolving stellar irradiation, which results, in particular, in photo-evaporation. The JADE code is benchmarked on GJ436 b, prototype of evaporating giants on eccentric, misaligned orbits at the edge of the hot Neptunes desert. We confirm that its orbital architecture is well explained by Kozai migration and unveil a strong interplay between its atmospheric and orbital evolution. During the resonance phase, the atmosphere pulsates in tune with the Kozai cycles, which leads to stronger tides and an earlier migration. This triggers a strong evaporation several Gyr after the planet formed, refining the paradigm that mass loss is dominant in the early age of close-in planets. This suggests that the edge of the desert could be formed of warm Neptunes whose evaporation was delayed by migration. It strengthens the importance of coupling atmospheric and dynamical evolution over secular timescales, which the JADE code will allow simulating for a wide range of systems.
We conducted a satellite search around the dwarf planet 1 Ceres using Hubble Space Telescope and ground-based Palomar data. No candidate objects were found orbiting Ceres in its entire stability region down to ~500km from the surface of Ceres. Assuming a satellite would have the same albedo as Ceres, which has a visual geometric albedo of 0.07-0.10, our detection limit is sensitive to satellites larger than 1-2 km in diameter.
We report a comprehensive analysis of the global spectrophotometric properties of Ceres using Dawn Framing Camera images collected from April to June 2015 during the RC3 and Survey mission phases. The single-scattering albedo of Ceres at 555 nm is 0.14$pm$0.04, the geometric albedo is 0.096$pm$0.006, and the Bond albedo is 0.037$pm$0.002. The asymmetry factors calculated from the best-fit two-term Henyey-Greenstein (HG) single-particle phase function (SPPF) show a wavelength dependence, suggesting that the phase reddening of Ceres is dominated by single-particle scattering rather than multiple scattering or small-scale surface roughness. The Hapke roughness parameter of Ceres is derived to be 20$^circpm$6$^circ$ with no wavelength dependence. The phase function of Ceres shows appreciably strong scattering around 90$^circ$ phase angle that cannot be fitted with a single-term HG SPPF, suggesting possible stronger forward scattering than other asteroids previously analyzed with spacecraft data. We speculate that such a scattering characteristic of Ceres might be related to its unique surface composition. We grouped the reflectance data into a 1$^circ$ latitude-longitude grid and fitted each grid independently to study the spatial variations of photometric properties. The albedo and color maps are consistent with previous studies. The SPPF over the surface of Ceres shows stronger backscattering associated with lower albedo and vice versa, consistent with the general trend among asteroids. The Hapke roughness parameter does not vary much across the surface of Ceres, except for the ancient Vendimia Planitia region that has a slightly higher roughness. Based on the wavelength dependence of the SPPF of Ceres, we hypothesize that its regolith grains either contain a considerable fraction of $lessapproxmu$m-sized particles, or are strongly affected by internal scatterers of this size.
In order to investigate the causes of different spectral slope in ccps, different grain-sizes of Ceres analogue mixtures were produced, heated to remove absorption of atmospheric water, and spectrally analyzed. First, the end-members which compose the Ceres surface (using the antigorite as Mg-phyllosilicate, the NH4-montmorillonite as NH4-phyllosilicate, the dolomite as carbonate and the graphite as dark component), were mixed, obtaining mixtures with different relative abundance, and identifying the mixture with the reflectance spectrum most similar to the average Ceres spectrum. The mixtures were obtained with grain size of 0-25 {mu}m, 25-50 mic and 50-100 mic, were heated and spectrally analysed at T= 300 K and T=200 K (typical for surface Ceres temperature during VIR observations). The most similar Ceres analogue mixture is composed of dolomite (18%), graphite (27%), antigorite (32%) and NH4-montmorillonite (29%) and the results of this work suggest that this mixture is more similar to the Ceres youngest region than to the Ceres average, in particular for the negative slope of spectrum. Small variation in the composition and grain size of end-members need to be considered, in addition to the occurrence of a dark component dispersed in fine size. Furthermore, the positive spectral slope that characterizes the mean Ceres spectrum can be obtained by the application of some processes simulating the space weathering on Ceres (as micro-meteoritic impacts and solar wind irradiation), i.e. laser and ion irradiation. As conclusion, youngest ccps on Ceresare probably composed by fresher and weakly processed mixture with fine dark material intimately dispersed: as a result, the reflectance spectra of youngest material show a negative slope in the 1.2-1.9 mic range. The redder slope observed in the older ccps is probably the consequence of the space weathering effects on fresher material
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