Journal Papers

1. M. Fenucci, G. F Gronchi, M. Saillenfest. Proper elements for resonant planet-crossing asteroids, Celestial Mechanics and Dynamical Astronomy 134 (2022). Abstract ▿▵

   
   Proper elements are quasi-integrals of motion, meaning that they can be considered constant over a certain timespan, and they permit to describe the long-term evolution with a few parameters. Near-Earth objects (NEOs) generally have a large eccentricity and therefore they can cross the orbits of the planets. Moreover, some of them are known to be currently in a mean-motion resonance with a planet. Thus, the methods previously used for the computation of main-belt asteroid proper elements are not appropriate for such objects. In this paper, we introduce a technique for the computation of proper elements of planet- crossing asteroids that are in a mean motion resonance with a planet. First, we numerically average the Hamiltonian over the fast angles while keeping all the resonant terms, and we describe how to continue a solution beyond orbit crossing singularities. Proper elements are then extracted from a frequency analysis of the averaged orbit-crossing solutions. We give proper elements of some known resonant NEOs, and provide comparisons with non- resonant models. These examples show that it is necessary to take into account the effect of the resonance for the computation of accurate proper elements

2. M. Fenucci, B. Novaković. Mercury and OrbFit packages for the numerical integration of planetary systems: implementation of the Yarkovsky and YORP effects, Serbian Astronomical Journal 204, pp 51-63 (2022). Abstract ▿▵

   
   For studies of the long-term evolution of small Solar System objects, it is fundamental to add the Yarkovsky and Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effects in the dynamical model. Still, the implementation of these effects in publicly available N-body codes is often lacking, or the effects are implemented using very simplified models. In this paper, we present an implementation of the coupled Yarkovsky/YORP effects in the mercury and OrbFit N-body codes. Along with these two effects, to properly model the asteroid spin state we have also included the effects of collisions and breakups. Given the stochastic nature of many effects included, the software is suitable for statistical dynamical studies. Here we explained the scientific aspect of the implementation, while technical details will be made freely available along with the source codes.

3. M. Fenucci, B. Novaković. The role of the Yarkovsky effect in the long-term dynamics of asteroid (469219) Kamo'oalewa, The Astronomical Journal, Volume 162, Number 6 (2021). Abstract ▿▵

   
   Near-Earth asteroid (469219) Kamo'oalewa (aka 2016 HO3) is an Earth co-orbital and a potential space mission target. Its short-term dynamics is characterized by a periodic switching between quasi-satellite and horseshoe configurations. Due to its small diameter of only about 36 meters, the Yarkovsky effect may play a significant role in the long-term dynamics. In this work, we addressed this issue by studying the changes in the long-term motion of Kamo'oalewa caused by the Yarkovsky effect. We used an estimation of the magnitude of the Yarkovsky effect assuming different surface compositions and introduced the semi-major axis drift by propagating orbits of test particles representing the clones of the nominal orbit. Our simulations showed that the Yarkovsky effect may cause Kamo'oalewa to exit from the Earth co-orbital region a bit faster when compared to a purely gravitational model. Nevertheless, it still could remain an Earth companion for at least 0.5 My in the future. Our results imply that Kamo'oalewa is the most stable Earth's co-orbital object known so far, not only from a short-term perspective but also on long time scales.

4. M. Fenucci, B. Novaković, D. Vokrouhlický, R. J. Weryk. Low thermal conductivity of the superfast rotator (499998) 2011 PT. Astronomy & Astrophysics 647, A61 (2021). Abstract ▿▵

   
   Context. Asteroids with a diameter of up to a few dozen meters may spin very fast and complete an entire rotation within a few minutes. These small and fast-rotating bodies are thought to be monolithic objects because the gravitational force due to their small size is not strong enough to counteract the strong centripetal force caused by the fast rotation. This argument means that the rubble-pile structure is not feasible for these objects. Additionally, it is not clear whether the fast spin prevents dust and small particles (regolith) from being kept on their surface.
   Aims. We develop a model for constraining the thermal conductivity of the surface of the small, fast-rotating near-Earth asteroids. This model may suggest whether regolith is likely present on these objects.
   Methods. Our approach is based on the comparison of the measured Yarkovsky drift and a predicted value using a theoretical model that depends on the orbital, physical and thermal parameters of the object. The necessary parameters are either deduced from statistical distribution derived for near-Earth asteroids population or determined from observations with associated uncertainty. With this information, we performed Monte Carlo simulations and produced a probability density distribution for the thermal conductivity.
   Results. Applying our model to the superfast rotator asteroid (499998) 2011 PT, we find that the measured Yarkovsky drift can only be achieved when the thermal conductivity K of the surface is low. The resulting probability density function for the conductivity is bimodal, with two most likely values being around 0.0001 and 0.005 W m⁻¹ K⁻¹. Based on this, we find that the probability that K is lower than 0.1 W m⁻¹ K⁻¹ is at least 95%. This low thermal conductivity might indicate that the surface of 2011 PT is covered with a thermal insulating layer, composed of a regolith-like material similar to lunar dust.
   

   
   

Conference Presentations

Event	Date	Title	Video	Slides
COOMOT	29/03/2022	The role of the Yarkovsky effect in the long-term dynamics of asteroid (469219) Kamo'oalewa
LPSC 53	09/03/2022	2016 GE1: An Extreme Example of Super-Fast Rotator with Very Low Thermal Inertia
LPSC 53	09/03/2022	The Asteroid Criticality Index: An Asteroid Ranking to Ease the Planning of Future Space Missions
IAU Symposium 364	21/10/2021	Proper elements for resonant planet-crossing orbits
7th PDC	27/04/2021	The low thermal conductivity of the super-fast rotator (499998) 2011 PT
LPSC 52	19/03/2021	Unexpected thermal properties of the near-Earth asteroid (499998) 2011 PT
Stardust-R GVW I	07/09/2020	The distribution of small near-Earth objects and the role of the Yarkovsky effect

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