Title:

Planet Formation and the Evolution of Gaseous Disks



Joan Najita
NOAO



Abstract:

Studies of circumstellar disks surrounding young stars have the 
potential to provide unique insights into the origins of planetary 
systems.  I will discuss two recent results on circumstellar disks in 
which the Spitzer Space Telescope has been instrumental: (1) our 
understanding of the nature of "transition objects", systems that may 
be currently undergoing giant planet formation and (2) the detection of 
mid-infrared atomic and molecular emission from T Tauri disks.  The 
latter results suggest new ways to probe the the gas dissipation 
timescale of disks and the extent of chemical processing and turbulent 
mixing in disks.