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[51.01] Two Distinct Populations of Kuiper Belt Objects

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.