Effect of main belt perturbers on asteroid-pair age estimation

Abstract

Context. Asteroid-pair age estimations are usually performed by backward integration of possible orbits of pair components, taking planetary perturbations into account along with the Yarkovsky effect. It is assumed that uncertainties coming from the backward integration process itself are small, so to reduce uncertainties in estimations, effort usually focuses on reducing uncertainties in the initial orbital elements and the dimensions of the pair components. Aims. This work aims to evaluate the role of the frequently ignored nonplanetary perturbers in asteroid-pair age estimation. When their role is not negligible, the ages of the youngest known pairs can be roughly re-estimated. Methods. The orbital evolution of several asteroid-pair components and the close approaches between components during the last ≈43 kyr are investigated. Initially, the force equations consisted of only planetary perturbers. The three largest main belt perturbers were added afterwards. Finally, as many as 262 massive main belt perturbers were included. The effect of main belters on age estimation is assessed by comparing the dates of the closest approaches between pair components. The range of the Yarkovsky effect is simulated very roughly, only for comparison purposes. Martes -2005 WW 113 , which was previously reported as very young, had slightly higher encounter velocities and longer nominal minimum distances, calling into question whether they could have formed within the interval studied or in some previous mutual encounter of pair components. Conclusions. The effect of main belt perturbers on asteroid-pair age estimation is buried in the huge age uncertainties caused by the Yarkovsky effect until the rotation direction of pair components is recognized.

Detailed Analysis of the Asteroid Pair (6070) Rheinland and (54827) 2001 NQ8

“…In principle, this additional interaction may result in more cases converging, perhaps extending slightly from the formal uncertainty of the age-distribution while not affecting the mean value ( Figure 6). More importantly, our tests have shown that the gravitational perturbations from the minor bodies included in our simulation, Ceres, Pallas, and Vesta, are indeed non-negligible (see conclusions in Galád 2012). If these bodies are excluded, the age estimate would shift by as much as 600-800 years toward older ages as seen, e.g., in solutions of Vokrouhlický & Nesvorný (2009.…”

“…Vokrouhlický & Nesvorný (2008) were thefirst to note theconvergence of (6070) Rheinland and (54827) 2001NQ8 at a very close distance in Cartesian space some 17kyr ago, interpreting this event as the physical origin of the two asteroids from a fission of their common parent body. Vokrouhlický & Nesvorný (2009), and later Vokrouhlický et al (2011) and Galád (2012), substantiated this solution by accounting for more details in the propagation model, such as mutual gravitational attraction of the two components during the short time interval in which they initially separated. In all of these publications, 17 kyr remained to be the nominally adopted age of the pair.…”

“…A confirmation would certainly have interesting implications on the fission mechanics of the parent body of the pair. We also note that Galád (2012) pointed out that an accurate modeling of the convergence of the 6070 and 54827 orbits in the past requires theinclusion ofgravitational perturbations of the most massive asteroids, aside fromthe obvious effects of planets.…”

“…The software package swift includes gravitational effects of major bodies in the solar system: the Sun and the planets. Given the results in Galád (2012), we also include gravitational perturbations from the dwarf planet Ceres, and the largest asteroids Vesta and Pallas. Their nominal orbital states were taken from AstDyS site and their masses were set to9.384 10 20 kg (Ceres; Russell et al 2016),2.59076 10 20 kg (Vesta; Russell et al 2012), and 2.06 10 20 kg (Pallas; Konopliv et al 2011).…”

Asteroid pairs: method validation and new candidates

“…After that, a number of dynamical studies were published (Pravec & Vokrouhlický 2009;Pravec et al 2019) that massively expanded the list of identified pairs. Other studies have shown the necessity of taking into account the most massive perturbers of the main belt (Ceres, Vesta, Pallas) in numerical calculations of the formation age of pairs (Galád 2012). At the same time, the findings by Vokrouhlický & Nesvorný (2008) and Žižka et al (2016) opened the road to the identification of very young asteroid pairs.…”