Early stages in the evolution of protoplanetary disks

Spitzer Space Telescope observations are an important tool for understanding the rst stages of protoplanetary disk evolution and planet formation. These observations indicate that primordial disks around young stars dissipate in a few millions of years (Myr), and this evolution shows a strong dependence on stellar masses. Recent studies in the Orion OB1 association have shown that second generation disks (debris disks) around A type stars due to collisional cascades between solid bodies can be formed within 10 Myr, while the lifetime of primordial disks around these objects is less than 3 Myr. In contrast, studies of the fraction of the disk-bearing stars in several star formation regions indicate that the characteristic time for primordial disk dissipation around low mass stars (spectral types K5 or later) is 5{7 Myr, showing an overall decrease in disk emission between 1 to 10 Myr. This contribution shows the main results from studies in the Orion OB1 stellar association combining SPITZER and 2MASS catalog data with optical data obtained in the CIDA Variability Survey.