Dr. Dana Backman

December 18, 2006

The Formation and Evolution of Planetary Systems: Placing Our Solar System in Context

We plan to trace the evolution of planetary systems at ages ranging from: (1) 3-10 Myr when stellar accretion from the disk terminates; to (2) 10-100 Myr when planets achieve their final masses via coalescence of solids and accretion of remnant molecular gas; to (3) 100-1000 Myr when the final architecture of solar systems takes form and frequent collisions between remnant planetesimals produce copious quantities of dust; and finally to (4) mature systems of age comparable to the Sun in which planet-driven activity of planetesimals continues to generate detectable dust. Our strategy is to use carefully calibrated spectral energy distributions and high-resolution spectra to infer the radial distribution of dust and the molecular hydrogen content of disks surrounding a sample of 300 solar-like stars distributed uniformly in log-age over 3 Myr to 3 Gyr.

The high precision and fine sampling of Spitzer spectral energy distributions can reveal both the existence of planets and their approximate masses and radial distributions through modeling of the dynamic effects of planets in sculpting planetesimal distributions and orchestrating their collision frequency. The size of our target list will enable us to characterize the diversity of planetary system architectures, providing a deeper appreciation of the range of possible outcomes of the planet formation process -- thus placing our own solar system in context.

Our Legacy program promises to provide: (1) new insight into problems of fundamental scientific and philosophical interest; (2) calibration with precision 2-3 times that of standard Spitzer data products, to the benefit of all Spitzer observers; (3) new numerical tools for simulating the dynamic history of forming solar systems; and (4) a rich database to stimulate follow-up observations with Spitzer, with existing and future ground-based facilities, and later with SIM, NGST, and TPF.