arXiv subjects

L. Dones

Publications and source records attributed to L. Dones.

4 recordsLinked to original sources

arXiv2026

Systematic and Statistical Uncertainties in the Non-Gravitational Acceleration of 3I/ATLAS

We present a detailed analysis of the trajectory of interstellar comet 3I/ATLAS, with emphasis on the determination of its non-gravitational acceleration (NGA) parameters and their associated uncertainties. Using astrometric observations spanning both pre- and post-perihelion phases, we compute orbital solutions assuming gravity-only, symmetric, delayed-peak, and asymmetric outgassing NGA models. To mitigate the effects of heterogeneous astrometric quality and potential tailward biases, we adopt a tiered uncertainty model that inflates the uncertainties of lower-fidelity observations, and assess solution robustness through validation against non-fitted data. We find clear evidence that NGA is required to reproduce the observations. Solutions obtained from pre- and post-perihelion arcs separately, however, yield mutually incompatible NGA parameters, suggesting either sensitivity to residual astrometric systematics or intrinsic limitations of constant parameter outgassing models. For the full data set, the inferred acceleration is in very good agreement with the latest JPL solution, supporting its use for physical interpretation and nucleus size estimates. Models incorporating delayed or asymmetric activity with respect to perihelion improve the fit relative to a symmetric prescription, suggesting that part of the observed asymmetry may be physical. We conclude that, while the NGA of 3I is robustly determined, systematic uncertainties arising from both residual astrometric biases and simplifications in the outgassing modeling prescriptions exceed the formal fitting errors, and should be taken into account when deriving physical properties such as the nucleus size.

astro-ph.EP↗

arXiv2017

Origin and Evolution of Short-Period Comets

Comets are icy objects that orbitally evolve from the trans-Neptunian region (the Kuiper belt and beyond) into the inner Solar System, where they are heated by solar radiation and become active due to sublimation of water ice. Here we perform end-to-end simulations in which cometary reservoirs are formed in the early Solar System and evolved over 4.5 Gyr. The gravitational effects of Planet 9 (P9), hypothesized to circle the Sun on a wide orbit, are included in some of our simulations. Different models are considered for comets to be active, including a simple assumption that comets remain active for Np(q) perihelion passages with perihelion distance q<2.5 au. The orbital distribution and number of active comets produced in our model is compared to observations. The orbital distribution of ecliptic comets (ECs) is well reproduced in models with Np(2.5)=500 and without P9. With P9, the inclination distribution of model ECs is wider than the observed one. We find that the known Halley-type comets (HTCs) have a nearly isotropic inclination distribution (with only a slight preference for prograde orbits). In our model, the HTCs appear to be an extension of the population of returning Oort-cloud comets (OCCs) to shorter orbital periods. The inclination distribution of model HTCs becomes broader with increasing Np, but the existing observational data are not good enough to constrain Np from orbital fits. Np(2.5)>1000 is required to obtain a steady-state population of large active HTCs that is consistent with observations. To fit the ratio of the returning-to-new OCCs, by contrast, our model implies that Np(2.5)<10, possibly because the detected long-period comets are smaller and much easier to disrupt than observed HTCs.

astro-ph.EP↗

arXiv2017

The Origin of Planetary Ring Systems

This chapter of the book Planetary Ring Systems addresses the origin of planetary rings, one of the least understood processes related to planet formation and evolution. Whereas rings seem ubiquitous around giant planets, their great diversity of mass, structure and composition is a challenge for any formation scenario. Recent advances in our understanding of ring and satellite formation and destruction suggest that these processes are interconnected, so that rings and satellites may be two aspects of the same geological system. However, no single theory seems able to explain the origin of the different planetary rings known in our Solar System, and it now seems evident that rings may result from a variety of processes like giant collisions, tidal stripping of comets or satellites, as well as planet formation itself. In order to build any theory of ring formation it is important to specify physical processes that affect the long-term evolution of rings, as well as to describe the different observations that any ring formation model should explain. This is the topic of section 2. In section 3, we focus our attention on Saturn's rings and their main properties, and then discuss the pros and cons of a series of ring formation models. We also discuss the link between rings and satellites. In section 4, we extend the discussion to the other giant planets (Jupiter, Uranus, and Neptune). Section 5 is devoted to new types of rings -- the recent discovery of rings orbiting small outer Solar System bodies (Centaurs), and the possible rings around extrasolar planets. In section 6, we conclude and try to identify critical observations and theoretical advances needed to better understand the origin of rings and their significance in the global evolution of planets.

astro-ph.EP↗

arXiv2011

Ridge Formation and De-Spinning of Iapetus via an Impact-Generated Satellite

We present a scenario for building the equatorial ridge and de-spinning Iapetus through an impact-generated disk and satellite. This impact puts debris into orbit, forming a ring inside the Roche limit and a satellite outside. This satellite rapidly pushes the ring material down to the surface of Iapetus, and then itself tidally evolves outward, thereby helping to de-spin Iapetus. This scenario can de-spin Iapetus an order of magnitude faster than when tides due to Saturn act alone, almost independently of its interior geophysical evolution. Eventually, the satellite is stripped from its orbit by Saturn. The range of satellite and impactor masses required is compatible with the estimated impact history of Iapetus.

astro-ph.EP↗