Formation of Planetary Cores at Type I Migration Traps

One of the long-standing unsolved problems of planet formation is how solid bodies of a few decimeters in size can "stick" to form large planetesimals. This is known as the "meter-size barrier." In recent years, it has become increasingly clear that some form of "particle trapping" must have played a role in overcoming the meter-size barrier. Particles can be trapped in long-lived local pressure maxima, such as those in anticyclonic vortices, zonal flows, or those believed to occur near ice lines or at dead zone boundaries. Such pressure traps are the ideal sites for the formation of planetesimals and small planetary embryos. Moreover, they likely produce large quantities of such bodies in a small region, making it likely that subsequent N -body evolution may lead to even larger planetary embryos. The goal of this Letter is to show that this indeed happens, and to study how efficient it is. In particular, we wish to find out if rocky/icy bodies as large as 10 M ⊕ can form within 1 Myr, since such bodies are the precursors of gas giant planets in the core accretion scenario.