Discovery of an asteroid family linked to (22) Kalliope and its moon Linus

TL;DR

This study identifies a new asteroid family linked to (22) Kalliope and its moon Linus, estimating the family's age and exploring the formation and evolution processes through various models.

Contribution

It is the first to report the Kalliope asteroid family and analyze its origin, age, and connection to Linus using hierarchical clustering and multiple dynamical models.

Findings

Kalliope family is approximately 900 million years old.

Linus and the family could have formed simultaneously.

Kalliope's shape was influenced by gravitational reaccumulation.

Abstract

According to adaptive-optics observations by Ferrais et al., (22) Kalliope is a 150-km, dense and differentiated body. Here, we interpret (22) Kalliope in the context of bodies in its surroundings. While there is a known moon Linus, with a 5:1 size ratio, no family has been reported in the literature, which is in contradiction with the existence of the moon. Using the hierarchical clustering method (HCM) along with physical data, we identified the Kalliope family. Previously, it was associated to (7481) San Marcello. We then used various models (N-body, Monte-Carlo, SPH) of its orbital and collisional evolution, including the break-up of the parent body, to estimate the dynamical age of the family and address its link to Linus. The best-fit age is (900+-100) My according to our collisional model, in agreement with the position of (22) Kalliope, which was modified by chaotic diffusion due to 4-1-1 three-body resonance with Jupiter and Saturn. It seems possible to create Linus and the Kalliope family at the same time, although our SPH simulations show a variety of outcomes, for both satellite size and the family size-frequency distribution. The shape of (22) Kalliope itself was most likely affected by gravitational reaccumulation of `streams', which creates characteristic hills observed on the surface. If the body was differentiated, its internal structure is surely asymmetric.