Here we report WFPC2 observations of the Quaoar-Weywot Kuiper belt binary. From these observations we find that Weywot is on an elliptical orbit with eccentricity of 0.14 { \pm} 0.04, period of 12.438 { \pm} 0.005 days, and a semi-major axis of 1.45 { \pm} 0.08 { \times} 104 km. The orbit reveals a surpsingly high Quaoar-Weywot system mass of 1.6{ \pm}0.3{ \times}10^21 kg. Using the surface properties of the Uranian and Neptunian satellites as a proxy for Quaoar's surface, we reanalyze the size estimate from Brown and Trujillo (2004). We find, from a mean of available published size estimates, a diameter for Quaoar of 890 { \pm} 70 km. We find Quaoar's density to be \rho = 4.2 { \pm} 1.3 g cm^-3, possibly the highest density in the Kuiper belt.
Categories: astro-ph.EP