Taxonomy of Centaurs and Trans-Neptunian objects

Trans-Neptunian objects (TNOs) and Centaurs display the widest color diversity in comparison to other small solar system bodies. The investigation of their properties can help in understanding the evolution of these objects. In this paper we propose a classification scheme based on multivariate statistical analysis of a homogeneous, high-quality set of B - V, V - R, V - I, and V - J color indices. Analyzing a sample of 51 objects and using a high confidence level, four groups have been identified and named: BB, BR, IR, and RR. The group BB contains objects with neutral color and RR those with very red color, while the others have intermediate behavior. We extend the analysis to 84 other objects for which three colors are available, obtaining a preliminary classification. A tentative interpretation of these groups in terms of surface characteristics is given.