Abstract
The leading source of uncertainty to predict the orbital motion of asteroid (99942) Apophis is a non-gravitational acceleration arising from the anisotropic thermal re-emission of absorbed radiation, known as the Yarkovsky effect. Previous attempts to obtain this parameter from astrometry for this object have only yielded marginally small values, without ruling out a pure gravitational interaction. Here we present an independent estimation of the Yarkovsky effect based on optical and radar astrometry which includes observations obtained during 2021. Our numerical approach exploits automatic differentiation techniques. We find a non-zero Yarkovsky parameter, A2 = (−2.899 ± 0.025) × 10−14 au d−2, with induced semi-major axis drift of (−199.0 ± 1.5) m yr−1 for Apophis. Our results provide definite collision probability predictions for the close approaches in 2029, 2036, and 2068.
Highlights
The leading source of uncertainty to predict the orbital motion of asteroid (99942) Apophis is a non-gravitational acceleration arising from the anisotropic thermal re-emission of absorbed radiation, known as the Yarkovsky effect
Computing the orbital dynamics of a Near Earth Asteroid (NEA) is a difficult problem, especially for assessing possible hazardous events where high precision is crucial: the NEA orbit is sensitive to several interactions, including post-Newtonian gravitational corrections, tidal effects and non-gravitational forces[3,4]
The results use an independent implementation for the planetary ephemeris and for the orbital dynamics of Apophis, as well as a different numerical integration technique
Summary
The leading source of uncertainty to predict the orbital motion of asteroid (99942) Apophis is a non-gravitational acceleration arising from the anisotropic thermal re-emission of absorbed radiation, known as the Yarkovsky effect. The leading source of orbital uncertainty for Apophis is the Yarkovsky effect[2,5,6,7], a dissipating non-gravitational interaction which induces a semi-major axis acceleration due to re-emission of the incident solar radiation[8,9,10,11]. We report independent results for a non-zero value of the unknown transverse Yarkovsky acceleration of Apophis, as determined from optical and radar astrometry data that include 2021 observations. The results use an independent implementation for the planetary ephemeris and for the orbital dynamics of Apophis, as well as a different numerical integration technique. While the underlying ephemeris and NEA models differ, the agreement of the values is a reproducible validation for the calculations, which is important and desirable specially for potentially hazardous objects
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