A von Mises–Fisher distribution for the orbital poles of the plutinos

Small solar system bodies have widely dispersed orbital poles, posing challenges to dynamical models of origin and evolution. To characterize the orbit pole distribution groups small it helps a functional form for model function. Previous studies used small-inclination approximation adopted variations normal inclination dispersions. Because is directional variable, its can be more appropriately modeled with statistics. We describe von Mises-Fisher (vMF) on surface unit sphere application bodies' poles. apply observed Plutinos. find mean located at 3.57 degrees longitude ascending node 124.38 (in J2000 reference frame), 99.7 per cent confidence cone half-angle 1.68 degrees. also estimate debiased 4.6 away, an 2.26 292.69 degrees, similar-size cone. The vMF concentration parameter Plutino inclinations (relative either estimate) 31.6. This resembles Rayleigh function width 10.2 Unlike previous models, naturally accommodates all physical (and no others), whereas or Gaussian must truncated range 0-180 Further work needed produce theory Plutinos against which compare observational results.