A Plausible Minimum Value of the Neptunian Tidal Dissipation Factor Estimated from Triton’s Astrometric Observations

Abstract

Tidal dissipation serves as the primary factor influencing the natural satellites’ orbital evolution and provides essential insights into planetary interior properties. The orbital evolution of the Neptune–Triton system due to tidal dissipation can be approximately determined from astrometrically observed positions of Triton over an extended period of time by using an accurate model of the orbital motion. The estimated accuracy of the Triton dynamical model we built and updated fit all the astrometric data. Based on the most complete weighting astrometric observations of Triton, a possible minimum value of the Neptunian tidal dissipation factor Q was estimated to be Q = (10.353 ± 2.517) × 10³ for a conventional value k₂ = 0.127 and a priori constraint of 10 × 10³. When the a priori constraints have a smaller value, the Q-solution also has a smaller value but a weak fit to observations. Therefore, the Q estimated from the existing astrometric data is a plausible minimum value with the current accuracy of astronomical observations. Based on the plausible minimum value of Q and the Love number k₂, it has been analyzed that Triton will reach Neptune’s Roche limit in approximately ~28 Gyr. This indicates a stable orbital evolution of Triton over a long period of time.