| Circumstellar disks generally are thought to be a common result of the star formation process. Analogy with the solar system suggests that these disks are protoplanetary disks, the likely formation sites of extra-solar planetary systems. While most of our knowledge regarding the properties of circumstellar disks comes from studies of isolated star-forming regions, most stars in our Galaxy likely form in dense embedded clusters. In this thesis, we have undertaken the first extensive program of L-band (3.4 mum) imaging surveys of eight nearby young clusters to determine the circumstellar disk dissipation timescale, and thus evaluate the overall likelihood and conditions of planet formation in the Galaxy.; The derived disk fractions in the youngest clusters lead us to suggest that the formation of circumstellar disks is indeed a common result of star formation, and is not dependent on environment (cluster vs. isolation). If no massive stars are present in the clusters, we show that the disks are not preferentially destroyed in the dense cluster environment. An examination of successively older clusters reveals that the overall disk fraction decreases with increasing cluster age. We show that the rate of decline also appears to be a function of stellar mass, such that disks surrounding high-mass stars have shorter lifetimes compared with disks surrounding lower mass stars. Finally, we derive the disk dissipation timescale and discuss the implications of this lifetime on the formation of planetary systems. |
