Circumstellar Disks: From Protostars to Planetary Systems

Ray Jayawardhana, Harvard University

The discovery of extrasolar planets has renewed interest in 
exploring the origin of planetary systems. Since planets form 
in dusty circumstellar disks, the study of disks around young 
and not-so-young stars provides important clues to the puzzle. 
Within the past two years, we have obtained high-resolution 
images of dust disks surrounding a handful of nearby young-adult 
stars. The images, made possible by a new generation of infrared 
and sub-millimeter instruments, show dust disks at different 
stages of evolution. Many of the disks appear to have central 
cavities and several show brightness asymmetries, possibly caused 
by newborn planets. They represent a missing link between the 
proto-planetary disks observed around even younger stars and the 
fully-grown planetary systems orbiting more mature stars. In at 
least one case, we may have caught a glimpse of the Kuiper Belt 
of an extrasolar planetary system.