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S.C. Tegler (N. Arizona U.), W. Romanishin (U. Oklahoma), G. Consolmagno (Vatican Observatory)
In our continuing BVR photometric survey of Kuiper belt objects (KBOs), we find that certain dynamical classes of KBOs exhibit very distinctive surface colors. In our data, 17 of 20 objects on large-inclination and large-eccentricity orbits with aphelion distances larger than 70 AU (a dynamically hot population) exhibit gray, B-R < 1.5, surface colors. In contrast, 21 of 21 classical KBOs on small-inclination and small-eccentricity orbits with perihelion distances larger than 40 AU (a dynamically cold population) exhibit red surface colors, B-R > 1.5. Finally, we find 22 Centaurs divide into two very different color populations, gray and red.
These observations are consistent with a primordial origin of KBO surface colors based on their original heliocentric distance. Gray objects may have formed closer to the Sun in regions subject to orbital perturbations by an outward migrating Neptune, resulting in hot orbits. Red objects formed farther from the Sun and would be only partly perturbed by Neptune (contributing to the Centaur population). The furthest objects (red surfaces, cooler orbits) would remain unperturbed.
Our observations were taken using CCD cameras on the Keck I 10-m telescope on Mauna Kea, Hawaii, the University of Arizona 2.3-m telescope on Kitt Peak, Arizona, and the Vatican Advanced Technology 1.8-m Telescope on Mt. Graham, Arizona. We thank the NASA Planetary Astronomy Program for support of our work (NAG5-12694) and the NASA Keck, Steward Observatory, and Vatican Observatory Time Allocation Committees for consistent allocation of telescope time.
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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.