Proto-planetary disks surrounding intermediate mass young stars

by Rens Waters (Astronomical Institute Amsterdam and Leuven)

Tuesday 19 Jan 2010, 10:30 → 12:00 Europe/Stockholm

FA31

The birth of planetary systems occurs in the gaseous disks that surround all young low and intermediate mass stars. This disk is a remnant of the star formation process, during which mass from the molecular cloud was transported to the proto-star through an accretion disk. When the mass accretion stops, the disk slowly dissipates, probably forming planets as it disperses. There is growing indirect evidence for ongoing planet formation in the disks that surround intermediate mass pre-main-sequence stars. For instance, the geometry of the disk changes through the formation of inner holes and/or disk gaps. Also, the composition of the dust particles in the disk change, forming minerals that are not present in interstellar space. Some disks are "self-shadowed", the shadow being cast by the inner rim of the disk which is puffed up due to the direct irradiation by the central star. Other disks are flaring, but the reason why some disks are self-shadowed and others flare is not clear. An intriguing question is the upper mass limit for stars that form planetary systems. There is evidence that stars as massive as 3-4 solar mass have remnant accretion disks that are still similar to those surrounding solar type T Tauri stars, but above that mass stars may have much different disk structures. Their rapid evolution and strong radiation field may inhibit planet formation.