CURRENT RESEARCH Chemical processes, environment, and dynamical evolution of the early solar system, comets, and preplanetary disks around young stars.

Planet formation has been known for many years to be tied to the accretion and evolution of gas and dust in disks around young HAeBe and T Tauri stars. This early stage of stellar evolution occurs after the shell around an embedded protostar collapses to form a preplanetary disk, revealing a pre-main-sequence star representative of the Sun when our solar system was forming.  This research program uses high-resolution spectra of ices, dust, and gas phase molecules in the disks of these pre-main sequence stars to study the physical conditions in the planet forming regions. In one project, infrared observations of gas phase molecules such as CO, H2, H3+, and H2O can be used to understand the chemical processes, environment, and dynamical evolution of ‘other solar systems’ that may be in the process of planet formation.  The abundance and excitation of these molecules can be used to clarify the time scales and initial conditions for planet building and may also provide a new technique to find protoplanets.  Infrared spectroscopic data are obtained from the Infrared Telescope (IRTF) and the 10 meter Keck Telescope on Mauna Kea.

Using high-resolution infrared observations of CO, we are providing the first direct observational verification of the stratification of gas and dust in disks around young stellar objects (YSOs).  How dust settles to the midplane is essential to understanding the initial constraints on planetesimal and planet formation. The physical structure of extended flared disks around YSOs depends on a variety of parameters including the extent of gas and dust mixing (i.e. turbulence), the rate of dust settling and the process of grain coagulation.  In general, dust settling and grain growth are expected to occur throughout the upper disk atmosphere until a balance is reached with diffusion (turbulence) near the midplane.  Even theoretically, these processes are only superficially understood as observational constraints have remained elusive.