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S.C. Tegler (Northern Arizona Univ), W. Romanishin (Univ Oklahoma)
Here we report on the results of a three-year survey of the broad-band optical colors of about one-quarter of the known Kuiper-belt objects using the Steward Observatory 2.3-m telescope and the Kitt Peak National Observatory 4.0-m telescope. We find that their B-V and V-R colors indicate the presence of two distinct populations: one consists of objects whose surface colors are only slightly redder than the color of the Sun, while the other consists of the reddest objects known in the Solar System1. The later population may have surfaces rich in complex carbon-bearing compounds. Our results can be summarized in the color-color diagram below. The extraordinarily red objects are in the upper right corner and the nearly solar-colored objects are in the lower left corner. The lack of any correlation between the colors of the objects and their orbital properties makes it difficult to point to a mechanism responsible for the two populations.
This research is supported by the NASA Origins of Solar Systems Program.
1 Tegler & Romanishin 1998, Nature 392, 49.
Associated graphic in PDF.