Detection of Semi-Major Axis Drifts in 54 Near-Earth Asteroids: New Measurements of the Yarkovsky Effect

TL;DR

This study measures and analyzes semi-major axis drifts in 54 Near-Earth Asteroids, primarily due to the Yarkovsky effect, providing insights into asteroid physical properties and non-gravitational forces affecting their orbits.

Contribution

It presents new measurements of Yarkovsky-induced orbital drifts in 54 NEAs, validating the effect's dominance and constraining asteroid physical properties through detailed orbital analysis.

Findings

42 NEAs show drift rates consistent with Yarkovsky predictions

12 NEAs exhibit higher drift rates possibly indicating additional forces

Typical Yarkovsky efficiency is around 10^-5

Abstract

We have identified and quantified semi-major axis drifts in Near-Earth Asteroids (NEAs) by performing orbital fits to optical and radar astrometry of all numbered NEAs. We focus on a subset of 54 NEAs that exhibit some of the most reliable and strongest drift rates. Our selection criteria include a Yarkovsky sensitivity metric that quantifies the detectability of semi-major axis drift in any given data set, a signal-to-noise metric, and orbital coverage requirements. In 42 cases, the observed drifts (~10^-3 AU/Myr) agree well with numerical estimates of Yarkovsky drifts. This agreement suggests that the Yarkovsky effect is the dominant non-gravitational process affecting these orbits, and allows us to derive constraints on asteroid physical properties. In 12 cases, the drifts exceed nominal Yarkovsky predictions, which could be due to inaccuracies in our knowledge of physical properties, faulty astrometry, or modeling errors. If these high rates cannot be ruled out by further observations or improvements in modeling, they would be indicative of the presence of an additional non-gravitational force, such as that resulting from a loss of mass of order a kilogram per second. We define the Yarkovsky efficiency f_Y as the ratio of the change in orbital energy to incident solar radiation energy, and we find that typical Yarkovsky efficiencies are ~10^-5.