2007AJ....134.2046J

We present U-band photometry of Kuiper Belt objects taken to further investigate their color-orbit systematics. As at longer optical and near-infrared wavelengths, the U-band colors of Kuiper Belt objects show a wide range and a unimodal distribution. We find no evidence that color systematics in the Kuiper Belt are strongly wavelength-dependent. This observation is consistent with control of the reflection characteristics by a single (but unidentified) reddening material. No evidence is found for blue/ultraviolet absorption that can arise from charge transfer transitions in hydrated minerals in some primitive (C-type) asteroids. In the classical KBOs alone the U-B and other color indices are most strongly correlated with the Tisserand parameter measured with respect to Neptune.