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M. Fulchignoni (Univ. Paris 7/DESPA, Obs. Paris), M.A. Barucci, A. Doressoundiram, J. Romon, M. Birlan (DESPA, Obs. Paris)
The outer regions of the Solar System have recently been found to be densely populated by Trans Neptunian Objects (TNOs) forming the so-called Edgeworth Kuiper belt. The study of these objects has rapidly evolved in the past few years especially from dynamical and theoretical points of view. Perturbations of TNOs due to the gravitational influence of the outer planets can inject some of these bodies into giant-planet crossing orbits characteristics of the Centaurs. The Centaurs, which show similar surface properties to TNOs, seem to be evolved from them.
The studies of physical and chemical properties of TNO population members are still limited by the difficulties in observing these faint objects. Most of the known TNOs have an apparent V magnitude lower than 23. In this range up to 105 objects are estimated to orbit in a zone between 30 and 50 AU from the Sun. Careful observational and image processing procedures have been used to obtain reliable photometric data of TNO’s. This is a very challenging task, so B-V, V-R, and V-I colours are available for no more than 25 objects and only 16 out of them have V-J colour determined.
We report the results of the first statistical analysis in order to investigate the surface properties of the TNOs population. Using the same statistical techniques applied to define the current asteroid taxonomy (based on colour data) we find a spreading of the objects between neutral colour to very red and, pushing further the analysis, the TNOs may be split into five groups. The differences in colour content are interpreted as a consequence of the TNOs evolution.