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 availa
ble with periods of $sim11.6$, $sim12.0$, $sim12.4$, and $sim12.8$ days. From the possible orbital solutions, system masses of $1.3-1.5pm0.1times10^{21}$ kg are found. These observations provide an updated density for Quaoar of $2.7-5.0{g cm$^{-3}$}$. In all cases, Weywots 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 Weywots eccentricity and semi-major axis. Accordingly, it appears that Weywots 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.
We present the first results of the Hubble Wide Field Camera 3 Test of Surfaces in the Outer Solar System (H/WTSOSS). The purpose of this survey was to measure the surface properties of a large number of Kuiper belt objects and attempt to infer compo
sitional and dynamical correlations. We find that the Centaurs and the low-perihelion scattered disk and resonant objects exhibit virtually identical bifurcated optical colour distributions and make up two well defined groups of object. Both groups have highly correlated optical and NIR colours which are well described by a pair of two component mixture models that have different red components, but share a common neutral component. The small, $H_{606}gtrsim5.6$ high-perihelion excited objects are entirely consistent with being drawn from the two branches of the mixing model suggesting that the colour bifurcation of the Centaurs is apparent in all small excited objects. On the other hand, objects larger than $H_{606}sim5.6$ are not consistent with the mixing model, suggesting some evolutionary process avoided by the smaller objects. The existence of a bifurcation amongst all excited populations argues that the two separate classes of object existed in the primordial disk before the excited Kuiper belt was populated. The cold classical objects exhibit a different type of surface which has colours that are consistent with being drawn from the red branch of the mixing model, but with much higher albedos.
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 Quaoars 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 Quaoars density to be rho = 4.2 {pm} 1.3 g cm^-3, possibly the highest density in the Kuiper belt.
We present here HST NICMOS F110W and F160W observations of Haumea, and its two satellites Hiiaka and Namaka. From the measured (F110W-F160W) colours of -1.209 +/-0.004, -1.48 +/- 0.06, and -1.4 +/- 0.2 mag for each object, respectively, we infer that
the 1.6 imcron water-ice absorption feature depths on Hiiaka and Namaka are at least as deep as that of Haumea. The light-curve of Haumea is detected in both filters, and we find that the infrared colour is bluer by approximately 2-3% at the phase of the red spot. These observations suggest that the satellites of Haumea were formed from the collision that produced the Haumea collisional family.
