Observation of the Disk of P

The first problem posed by the existence of the disk around P Pic is the age of the star: P Pic is a star that is several hundred million years old, or more than ten times the lifetime of the disks that we have described. In the absence of any mechanism of renewal, the disk should have dissipated; its presence therefore implies the existence of a process for the renewal of the disk from the initial reservoir. The process by which the material of the disk is accreted into planetoids and small bodies, just before the T-Tauri phase, provides a natural solution to this problem. The material accreted into these objects may subsequently re-supply the disk, after the T-Tauri phase, by evaporation close to the star, or through the effects of collisions.

Figure 5.22 shows the disk of P Pic, as observed by the HST. It has been detected with a diameter of nearly one thousand AU, and the enlargement of the central

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