Influence of the Yarkovsky force on Jupiter Trojan asteroids

TL;DR

This study examines how the Yarkovsky force affects the long-term orbital evolution and stability of Jupiter Trojan asteroids, especially smaller ones, revealing size-dependent depletion and complex rotational effects.

Contribution

It provides the first detailed numerical analysis of the Yarkovsky effect on Jupiter Trojans, highlighting size and rotation-dependent orbital changes over a billion-year timescale.

Findings

Objects with R ≤ 1 km are significantly affected by the Yarkovsky force.

Small Trojans are depleted over hundreds of millions of years, altering size distribution.

The Yarkovsky effect influences orbital distribution and ejection rates based on rotation sense.

Abstract

Aims. We investigate the influence of the Yarkovsky force on the long-term orbital evolution of Jupiter Trojan asteroids. Methods. Clones of the observed population with different sizes and different thermal properties were numerically integrated for 1 Gyr with and without the Yarkovsky effect. The escape rate of these objects from the Trojan region as well as changes in the libration amplitude, eccentricity, and inclination were used as a metric of the strength of the Yarkovsky effect on the Trojan orbits. Results. Objects with radii $R\leq$1 km are significantly influenced by the Yarkovsky force. The effect causes a depletion of these objects over timescales of a few hundred million years. As a consequence, we expect the size-frequency distribution of small Trojans to show a shallower slope than that of the currently observable population ($R$ $\gtrsim$ 1 km), with a turning point between $R$ = 100 m and $R$ = 1 km. The effect of the Yarkovsky acceleration on the orbits of Trojans depends on the sense of rotation in a complex way. The libration amplitude of prograde rotators decreases with time while the eccentricity increases. Retrograde rotators experience the opposite effect, which results in retrograde rotators being ejected faster from the 1:1 resonance region. Furthermore, for objects affected by the Yarkovsky force, we find indications that the effect tends to smooth out the differences in the orbital distribution between the two clouds.