Authors: Harold F. Levison & S. Alan Stern

Status: To appear in Astronomical Journal.

Abstract: We present a new analysis of the currently available orbital elements for the known Kuiper belt objects. In the main, non-resonant Kuiper belt we find a statistically significant relationship between an object's absolute magnitude (H) and inclination (i). Objects with H<6.5 (radii >170 km for a 4% albedo) have higher inclinations than those with H>6.5 (radii <170 km). We have shown that this relationship is not caused by any obvious observational bias. We argue that the main Kuiper belt consists of the superposition of two distinct distributions. One is dynamically hot with inclinations as large as ~35^o and absolute magnitudes as bright as 4.5. The other is dynamically cold with i<~5^o and H>6.5. The dynamically cold population is most likely dynamically primordial. We speculate on the potential causes of this relationship.

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