It can be argued that no one has done more to shape our current view of the origin and evolution of planetary systems than Douglas N. C. Lin (Professor of Astronomy and Astrophysics at the University of California, Santa Cruz). He has made fundamental contributions to the study of the physics of astrophysical disks: from gaseous protoplanetary disks, to Saturn's rings, spiral galaxy disks, and the accretion rings around black holes that power quasars. Doug has an extensive publication record of over 300 papers on a large variety of topics with many different collaborators. However, his greatest impact has been in the field of planet formation and the booming field of extrasolar planets.
Early on, Doug realized that accretion disk modeling with turbulent angular momentum transport needs to be applied to protoplanetary disks in order to understand the environment for planet formation. He developed the formalism (the so-called "alpha" models) that is still used today to describe the evolution of these disks.
Many years before the discovery of exoplanets, Doug worked with Jim Pringle and John Papaloizou, among others, to pioneer work on the interaction between accretion disks and massive objects, including planets, in orbit about their parent stars. With John Papaloizou, he worked to develop the theory of how planets embedded in gaseous disks would create strong trailing shocks leading to transport of angular momentum, the opening of gaps, and the migration of planets. In this way he developed a mechanism for the creation of the so-called "Hot Jupiters." Doug's most cited paper (with over 500 citations) is on the origins of the first exoplanet discovered, the Hot Jupiter 51 Peg.
In recent years Doug, along with Shigeru Ida, formulated the concept of "population synthesis modeling." Through a continuing series of papers, he has developed and improved upon a comprehensive Monte Carlo code that attempts to combine all of the messy planet formation processes in an end-to-end model for predicting an unbiased population of planets. This is now the preferred framework, especially among observers, for interpreting observed distributions.
Although Doug's recent efforts have focused on planetary dynamics and formation, he has contributed significantly to the field of galactic dynamics. With Sandy Faber, Doug studied the structure and formation of dwarf elliptical galaxies. In addition, he was one of the first researchers to consider the effects of ram pressure stripping on the creation of dwarf ellipticals. Finally, Doug has studied the motions of the Magellanic Cloud (with Donald Lynden-Bell, Burton Jones, and others) to help build our understanding of the structure of the Milky Way, including its dark matter halo.