2004 Annual Science Report
University of Colorado, Boulder Reporting | JUL 2003 – JUN 2004
Origins of Planetary Systems
How are planets born? In what type of environment, and under what conditions do most stars (and associated planetary systems) form? How do grains and gas in proto-planetary systems evolve from interstellar properties to solid bodies? I have been using the world’s largest telescopes (such as the Keck 10m and Gemini 8m telescopes) to search for answers at wavelengths between 0.5 and 20 µm.
Most stars form in rich clusters that include massive stars where ultraviolet (UV) radiation and close passages of sibling stars pose hazards to proto-planetary disks. However, these hazards predominantly impact the outer parts of circumstellar environments; the inner 10 Astronomical Unit regions can survive for 10s of millions of years. Henry Throop (SWRI) and I are finding that UV radiation fields may actually stimulate planetesimal formation. While radiation and dynamical processes can rapidly strip away outer disks, exposure to UV may promote condensation of solid bodies in the planetary zone. UV preferentially removes light gases and small grains; large particles become concentrated in the disk mid-plane and can rapidly evolve toward gravitational instabilities.
Some aspects of planet formation and disk evolution require precision photometry with small telescopes. I started a program to monitor variations to select a sample of young stars with nearly edge-on disks whose gas and grain properties can be further probed by UV, visual, and near-infrared spectroscopy.