ESO-VLT large program on Centaurs and TNOs
Résumé
The ESO Large Program on the study of Trans-Neptunian Objects (TNOs) and Centaurs has been carried out during the last two years (April 2001-March 2003) at the Paranal (Very Large Telescope VLT) and La Silla (New Technology Telescope NTT) observatories of the European Southern Observatory (ESO) in Chile. The aim of the Large Program was to investigate the physical properties of this population composed of cold and primitive objects. Results has been obtained for multi-wavelength imaging BVRI and JHK filters of ~70 and ~30 objects respectively as well as for low-dispersion visible and near-IR spectroscopy of ~12 objects. The photometric results and analyses of the relative correlations between colours photometric gradients and dynamical properties of the objects will be presented and discussed. The spectroscopic results have been interpreted with models computed using geographical mixture of organics minerals and ices in order to constrain the surface composition. The spectra show a wide range of slopes some are featureless with almost constant gradients over the visible-NIR range while others show absorption signatures of ices. The limit and the utility of the ground-based observations will be discussed together with the necessity of a space exploration.