 The nebula continues to orbit the pre-main-sequence star for a period of until it is cleared out by radiation pressure and other processes.Second generation dust may then be generated about the star by collisions between the planetesimals, which forms a disk out of the resulting debris.At some point during their lifetime, at least 45% of these stars are surrounded by a debris disk, which then can be detected by the thermal emission of the dust using an infrared telescope.