Structure and Evolution of Circumstellar Disks Around Young Stars:
Placing Our Solar System in Context 

Michael R. Meyer 
Steward Observatory
University of Arizona

Over the past 10 years abundant evidence has emerged that many 
(if not all) stars are born with circumstellar disks.   Understanding the 
evolution of disks can provide strong constraints on theories of planet 
formation.  In addition, characterizing the physical properties of disks 
can provide valuable insight into the star formation process.  While concensus 
is emerging concerning the the early evolution of accretion disks (tau < 10 Myr)
and the characterization of older debris disks (tau > 1 Gyr) continues at a 
rapid pace little is known about the transition between these two extremes 
thought to occur during the epoch of planet formation.  Recent studies 
undertaken with ground and space-based observatories are helping to address 
questions concerning the structure and evolution of disks around young stars.  
New results from these programs will be presented and directions for future 
research will be discussed.  In particular, the promise of NASA's Space 
Infrared Telescope Facility, set for launch in 2002, to help us understand 
the formation and evolution of planetary systems will be summarized.