The Inclination Distribution of the Kuiper Belt

We develop a general method for determining the unbiased inclination distribution of the Kuiper belt using only the inclination and latitude of discovery of known Kuiper belt objects (KBOs). These two parameters are well determined for each discovered object, so we can use all 379 known KBOs (as of 2001 January 1)Èwithout knowing the objectÏs precise orbit, area, detection efficiency, or the latitudinal coverage of the survey that found the objectÈto determine the inclination distribution. We Ðnd that a natural analytic form for the inclination distribution is a sine of the inclination multiplied by a Gaussian. The inclination distribution of all KBOs is well Ðtted by sin i multiplied by a sum of two Gaussians with widths and 15¡ ^ 1¡. For this inclination distribution, the Kuiper belt has an e†ective area of ~.2 `.8 deg2 and a FWHM of 12.5¡^ 3.5¡ in latitude. The inclination distribution of the di†erent ~1100 `1500 dynamical classes appear di†erent. The Plutinos are well Ðt by sin i mulitplied by a single Gaussian of width the classical KBOs cannot be Ðt to a single Gaussian but are well Ðt by sin i multiplied ~1.8 `2.5, by the sum of two Gaussians of widths and 17¡ ^ 3¡, and the scattered KBOs are poorly Ðt by ~.6 `.2 sin i multiplied by a single Gaussian of width 20¡ ^ 4¡. The poor Ðt of the scattered objects is possibly a result of limitations of the method in dealing with large eccentricities. The e†ective areas of the Plutinos, classical KBOs, and scattered KBOs are 9300^ 1800, 6100 ^ 2100, and 17000 ^ 3000 deg2, respectively. The FWHMs are 23¡ ^ 5¡, and 44¡ ^ 10¡, respectively. In all cases, the inclinations of the ~3.6 `2.0, Kuiper belt objects appear larger than expected from dynamical simulations of possible perturbations.