How typical is our Solar System? The issue of how planetary systems form and dynamically evolve is one of the oldest unsolved problems in astronomy. In the past few years, remarkable observational clues have been found in various newly discovered structures such as a vast reservoir of large comet-like icy bodies beyond Neptune, potentially planet-forming disks of gas and dust around newly forming stars and unusual planetary systems around many nearby mature stars. These discoveries challenge many aspects of what had become the "standard model" of planet formation, requiring, for example, mechanisms to create the intricate and disturbed structure in the cometary disk beyond Neptune and to affect not only the eccentricities ("shapes") of orbits but to induce spiralling inward or outward of planets in our own system as well as those around other stars. It is still widely believed, however, that the cores of most planets are formed from the accumulation of much smaller bodies ("planetesimals") reminiscent of present-day comets and asteroids. Due to the generally chaotic nature of their dynamics, the currently most powerful theoretical method for understanding the formation and dynamical evolution of such systems is to construct computer models to numerically follow the orbits of large numbers of gravitationally interacting bodies for millions to billions of years, including the effects of interactions with the gas disk and/or physical collisions among the bodies.
Many of the problems I am studying with my graduate students and international collaborators utilize a very efficient computer software package called SWIFT, developed by H. Levison (SouthWest Research Institute) and me, and widely used internationally. We are incorporating a variety of methods to more efficiently model the interaction of large bodies ("protoplanets") with a population of smaller bodies and are now poised to tackle pressing problems relating to the late stages of planet formation which have been hitherto computationally intractable. These include: 1) Further comparison of theoretical models (incorporating e.g. the outward migration of Neptune due to planetesimal scattering) with of the observed structure of the trans-Neptunian region. 2) Extensive simulations of the mid- to late stages of the formation of Earth-like planets. 3) Further simulations of the late stages of giant planet formation in our own and extrasolar systems, and 4) Modelling of the influence of the planet-building process and the star's galactic environment on the formation of the cometary reservoirs.
Sample of some of my recent refereed publications on these topics:
- McNeil, D., Duncan, M., and Levison, H. 2005, "Effects of Type I Migration on Terrestrial Planet Formation".
Astronomical Journal, 130, 2884-2899.
- Dones, L., Weissman, P.R., Levison, H.F. and Duncan, M.J. 2004, "Oort Cloud Formation and Dynamics".
Invited and refereed review chapter in "Comets II", eds M. Festou, H.U. Keller and H.A. Weaver (University of Arizona Press: Tucson), 153-174.
- Duncan, M.J., Levison, H.F. and Dones, L. 2004, "Dynamical Evolution of Ecliptic Comets".
Invited and refereed review chapter in "Comets II", eds M. Festou, H.U. Keller and H.A. Weaver (University of Arizona Press: Tucson), 193-204.
- Thommes, E. W., Duncan, M. J. and Levison, H.F. 2003, "Oligarchic Growth of Giant Planets".
Icarus, 161, 431-455.
- Thommes, E. W., Duncan, M. J. and Levison, H.F. 2002, "The Formation of Uranus and Neptune Among Jupiter and Saturn".
Astron. Journal, 123, 2862-2883.
- Quintana, E.V., Lissauer, J.J., Chambers, J.E., and Duncan, M.J. 2002, "Terrestrial Planet Formation in the Alpha Centauri System".
Astrophysical Journal, 576, 982-996.