The Mass, Orbit, and Tidal Evolution of the Quaoar-Weywot System

TL;DR

This study uses new adaptive optics data to refine the orbit, mass, and density of the Quaoar-Weywot system, and analyzes its tidal evolution, suggesting Weywot's eccentricity was likely set after formation.

Contribution

It provides the first detailed orbital and physical parameters for the Quaoar-Weywot system and models its tidal evolution, revealing insights into its formation and dynamical history.

Findings

Four possible orbital solutions due to aliasing.

System mass estimated at 1.3-1.5×10^21 kg.

Weywot's orbit is eccentric with e~0.13-0.16.

Abstract

Here we present new adaptive optics observations of the Quaoar-Weywot system. With these new observations we determine an improved system orbit. Due to a 0.39 day alias that exists in available observations, four possible orbital solutions are available with periods of $\sim11.6$, $\sim12.0$, $\sim12.4$, and $\sim12.8$ days. From the possible orbital solutions, system masses of $1.3-1.5\pm0.1\times10^{21}$ kg are found. These observations provide an updated density for Quaoar of $2.7-5.0{g cm$^{-3}$}$. In all cases, Weywot's orbit is eccentric, with possible values $\sim0.13-0.16$. We present a reanalysis of the tidal orbital evolution of the Quoaor-Weywot system. We have found that Weywot has probably evolved to a state of synchronous rotation, and have likely preserved their initial inclinations over the age of the Solar system. We find that for plausible values of the effective tidal dissipation factor tides produce a very slow evolution of Weywot's eccentricity and semi-major axis. Accordingly, it appears that Weywot's eccentricity likely did not tidally evolve to its current value from an initially circular orbit. Rather, it seems that some other mechanism has raised its eccentricity post-formation, or Weywot formed with a non-negligible eccentricity.