The Yarkovsky and YORP Effects

TL;DR

This paper reviews the Yarkovsky and YORP effects, which are subtle forces and torques caused by sunlight that influence the orbits and rotations of small celestial bodies, with implications for planetary science.

Contribution

It provides a comprehensive review of recent findings on the Yarkovsky and YORP effects and discusses future research directions in planetary science.

Findings

Yarkovsky effect causes measurable orbital changes over long timescales.

YORP effect influences rotation rates and obliquities of small bodies.

Recent studies have used these effects to solve planetary science mysteries.

Abstract

The Yarkovsky effect describes a small but significant force that affects the orbital motion of meteoroids and asteroids smaller than $30-40$ kilometers in diameter. It is caused by sunlight; when these bodies heat up in the Sun, they eventually re-radiate the energy away in the thermal waveband, which in turn creates a tiny thrust. This recoil acceleration is much weaker than solar and planetary gravitational forces, but it can produce measurable orbital changes over decades and substantial orbital effects over millions to billions of years. The same physical phenomenon also creates a thermal torque that, complemented by a torque produced by scattered sunlight, can modify the rotation rates and obliquities of small bodies as well. This rotational variant has been coined the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect. During the past decade or so, the Yarkovsky and YORP effects have been used to explore and potentially resolve a number of unsolved mysteries in planetary science dealing with small bodies. Here we review the main results to date, and preview the goals for future work.