Colors of Kuiper Belt objects : the relationship between KBO colors and Kuiper Belt plane inclination

Abstract

A large population of small, icy bodies orbits the sun just beyond Neptune, known as the Kuiper Belt. These objects, thought to be the progenitors of short period comets, could provide a sample of primordial material in our solar system, constraining solar system formation models. The colors of Kuiper belt objects (KBOs) can indicate different surface compositions, environmental conditions, or formation characteristics within the Kuiper Belt. Data from the Deep Ecliptic Survey (DES, Millis et al. 2002) have been used to determine the plane of the Kuiper Belt, identifying "core" and "halo" populations with respect to this plane (Elliot et al. 2005). By comparing the colors of objects as a function of inclination, trends can be established distinguishing the core and halo populations. Sloan g', r' and i' observations were obtained from the 6.5-m Clay telescope at Las Campanas Observatory of 14 KBOs, which were combined with previously published data to examine the transition between these two populations as a function of color. For inclination bins containing equal numbers of KBOs, the percentage of red objects (B-R > 1.56, where B-R = 1.56 is the median of the sample) decreases with increasing inclination in a smooth, but nonlinear fashion.

(cont.) This steady decrease could imply that the objects at lower inclinations are less perturbed than those at higher inclinations, resulting in redder surfaces. Additionally, the objects at lower inclinations could represent a primordial population of objects, available to study and to constrain the formation models of the solar system.