Asteroid families in the first-order resonances with Jupiter

Abstract

Asteroids residing in the first‐order mean motion resonances with Jupiter hold important information about the processes that set the final architecture of giant planets. Here, we revise current populations of objects in the J2/1 (Hecuba‐gap group), J3/2 (Hilda group) and J4/3 (Thule group) resonances. The number of multi‐opposition asteroids found is 274 for J2/1, 1197 for J3/2 and three for J4/3. By discovering a second and third object in the J4/3 resonance (186024) 2001 QG207 and (185290) 2006 UB219, this population becomes a real group rather than a single object. Using both hierarchical clustering technique and colour identification, we characterize a collisionally born asteroid family around the largest object (1911) Schubart in the J3/2 resonance. There is also a looser cluster around the largest asteroid (153) Hilda. Using N‐body numerical simulations we prove that the Yarkovsky effect (infrared thermal emission from the surface of asteroids) causes a systematic drift in eccentricity for resonant asteroids, while their semimajor axis is almost fixed due to the strong coupling with Jupiter. This is a different mechanism from main belt families, where the Yarkovsky drift affects basically the semimajor axis. We use the eccentricity evolution to determine the following ages: (1.7 ± 0.7) Gyr for the Schubart family and ≳4 Gyr for the Hilda family. We also find that collisionally born clusters in the J2/1 resonance would efficiently dynamically disperse. The steep size distribution of the stable population inside this resonance could thus make sense if most of these bodies are fragments from an event older than ≃1 Gyr. Finally, we test stability of resonant populations during Jupiter's and Saturn's crossing of their mutual mean motion resonances. In particular, we find primordial objects in the J3/2 resonance were efficiently removed from their orbits when Jupiter and Saturn crossed their 1:2 mean motion resonance.

ALBEDOS OF SMALL HILDA GROUP ASTEROIDS AS REVEALED BYSPITZER

“…Thus, the decrement of small Hilda group asteroids could be explained via an intense collisional period, such as occurred in the late heavy bombardment epoch in the early solar system followed by a long period of low collisional activity. The age estimate of 4 Gyr for the Hilda family (Broz & Vokrouhlicky 2008), a dynamical subgroup of the Hilda asteroid group (see Section 4.4), lends credence to the later hypothesis.…”

“…The discovery of distinct dynamical families within the Hilda group by Broz & Vokrouhlicky (2008) necessitates examination of whether or not variations in albedo observed in our sample (Table 2) are indicative of dynamical family membership instead. Utilizing the hierarchical clustering method (Zappalà et al 1990) which uses proper elements of asteroids and searches phase space for clusters of objects with similar velocities, Broz & Vokrouhlicky (2008) identified two distinct dynamical families within the Hilda orbital group.…”

“…Utilizing the hierarchical clustering method (Zappalà et al 1990) which uses proper elements of asteroids and searches phase space for clusters of objects with similar velocities, Broz & Vokrouhlicky (2008) identified two distinct dynamical families within the Hilda orbital group. Of these two dynamical families, Hilda and Schubart, identified by Broz & Vokrouhlicky (2008), only the Schubart dynamical family contributes significantly to our Hilda asteroid group sample. The 16 members of the Schubart family present in our sample follow the same albedo trend as seen within the rest of the Hilda asteroid group as illustrated in Figure 3.…”

Low-frequency Slivan states in the outer main belt?

“…We find that the distant Themis family represents an ideal population of asteroids where these low-frequency Slivan states could be sought in the future. Alternatively, one could also consider the Schubart family among Hilda asteroids (e.g., Brož & Vokrouhlický 2008), or even the low-inclination population among Jupiter Trojans. The latter is not surprising, because Jupiter's spin axis itself is possibly pushed to its 3…”

Interior Resonance Periodic Orbits in Photogravitational Restricted Three-body Problem

“…This is because of their orbital proximity to Jupiter (Brož and Vokrouhlicky [32]). In this study, we consider the more massive primary as a source of radiation and the smaller primary as an oblate spheroid.…”