The upper limit of its total mass in the outer Solar System is \(10^-5M_\oplus\) (Moro-Martin 2012). So, the dynamics of the system

is governed by the gravitational star-planet and planet-planet interactions. In T Tauri stars, instead, the interaction of a planet with the gaseous disc becomes relevant and should be taken into account. The gravitational tidal interaction between the planet and the disc leads to the migration of the planet. The orbital elements learn more of planets are subjected to the continuous changes due to the energy and angular momentum exchange between the planet and the disc. This in turn leads to the phenomenon of resonant capture, providing one of the plausible scenarios in which the observed commensurabilities could form. Planetary Migration Gaseous discs around T Tauri stars are likely sites of planet formation (Hartmann et al. 1998). The planetary objects forming or recently formed within such discs interact gravitationally with the gas producing an exchange of energy and angular momentum between the protoplanet

and the disc. This exchange results in torques acting on the protoplanets due to waves, generated at Lindblad resonances and corotation torques generated near the orbit of the planet (Goldreich HDAC inhibitor and Tremaine 1979). The disc-planet interactions can influence the BMS202 protoplanet orbits, changing their semi-major axis (Ward 1997), eccentricity (Goldreich and Sari 2003) and inclination (Thommes and Lissauer 2003). The evolution of the semi-major axis of the protoplanet (called planetary or orbital migration) increases the protoplanet mobility in the disc. The increased mobility facilitates the mass growth of the protoplanet and, for protoplanets in the giant

planet mass range it provides a potential explanation of the formation of the so-called “hot Jupiters”. Finally, the convergent migration of planets or protoplanetary cores is one of the most promising processes to explain the formation of resonant configurations. The outcome of the disc-planet interaction (-)-p-Bromotetramisole Oxalate depends on the rate and the direction of the migration, which in turn are determined by the planet mass and the disc parameters (see Eqs. 6–8). The migration rates for planets of different mass have been estimated by a number of authors, see for example the review by Papaloizou and Terquem (2006) and, most recently, the paper by Paardekooper et al. (2011). Depending on the planet masses and on the disc properties, three main regimes of orbital migration can be distinguished. Type I Migration For low-mass planets (up to several Earth masses for standard Solar nebula parameters) the disc undergoes small linear perturbations that induce density waves propagating away from the planet. The angular momentum transported away by these waves results in a rapid orbital migration called type I migration (Ward 1997).