Structure and evolution of protoplanetary disks: Observing planet formation in action

ABSTRACT: 
Protoplanetary disks are the birth places of planetary systems. Most
young stars are surrounded by such planet forming disks. The onset of
the processes associated with planet formation significantly alter the
radial and vertical structure of the disks, modify the gas and dust
content in them, and cause the dust grains in the disks to crystallize
and grow in size. Observationally, these structural and
evolutionary changes are best studied at infrared wavelengths. We have
obtained and analysed mid-infrared (5-40 micron) spectra of several
hundred young protoplanetary disks from the nearby star forming
regions using the Spitzer space telescope. I will present the results
and discuss their implications for our understanding of the early
stages of planet formation and the evolution and eventual dissipation
of protoplanetary disks.