The Yarkovsky effect on the long-term evolution of binary asteroids

TL;DR

This paper develops an analytical model for the Yarkovsky effect on binary asteroids, revealing its significant influence on their long-term orbital evolution and potential to produce observable phenomena.

Contribution

The paper introduces a new analytical model for the binary Yarkovsky effect, considering both components and verifying it with numerical simulations, predicting new evolutionary paths for binary asteroids.

Findings

Yarkovsky force can alter mutual orbits when spin and orbital periods differ.

Prograde secondaries migrate inward faster than other processes.

Retrograde secondaries tend to migrate outward, possibly forming asteroid pairs.

Abstract

We explore the Yarkovsky effect on small binary asteroids. While significant attention has been given to the binary YORP effect, the Yarkovsky effect is often overlooked. We develop an analytical model for the binary Yarkovsky effect, considering both the Yarkovsky-Schach and planetary Yarkovsky components, and verify it against thermophysical numerical simulations. We find that the Yarkovsky force could change the mutual orbit when the asteroid's spin period is unequal to the orbital period. Our analysis predicts new evolutionary paths for binaries. For a prograde asynchronous secondary, the Yarkovsky force will migrate the satellite towards the location of the synchronous orbit on ~100 kyr timescales, which could be faster than other synchronization processes such as YORP and tides. For retrograde secondaries, the Yarkovsky force always migrates the secondary outwards, which could produce asteroid pairs with opposite spin poles. Satellites spinning faster than the Roche limit orbit period (e.g. from ~4h to ~10h) will migrate inwards until they disrupt, reshape, or form a contact binary. We also predict a short-lived equilibrium state for asynchronous secondaries where the Yarkovsky force is balanced by tides. We provide calculations of the Yarkovsky-induced drift rate for known asynchronous binaries. If the NASA DART impact broke Dimorphos from synchronous rotation, we predict that Dimorphos's orbit will shrink by \dot a ~ 7 cm/yr, which can be measured by the Hera mission. We also speculate that the Yarkovsky force may have synchronized the Dinkinesh-Selam system after a possible merger of Selam's two lobes.