Evolution of Planets in Disks

The main properties of the observed extrasolar planets are reviewed with respect to their relevance to the formation scenario of planetary systems. Results of numerical computations of embedded planets in viscously evolving disks are presented. Emphasis is given to the accretion and migration process. New calculations on inviscid disks are shown. The second part of the talk concentrates on resonant planetary systems. Among the observed extra-solar systems there are 3 confirmed cases, Gl 876, HD 82943 and 55 Cnc, where the planets orbit their central star in a low order mean motion resonance. Results of numerical simulations modeling the formation and evolution of such systems are presented. Since the first discovery of extrasolar planets around main sequence stars in 1995, their number has risen to over 100 planets today. For an always up-to-date list see e.g. Apart from two discoveries by the transit method of OGLE-objects (Konacki et al. 2003; Dreizler et al. 2003), all others have been found by radial velocity measurements. Among all systems, there are at least 12 planetary systems with two or more planets; a summary of their properties has recently been given by Marcy et al. (2003). Longer observations to study trends in velocity curves may still increase this number. Of all stars investigated, planets have been found so far around about 7 %. The orbital properties of these planetary systems display features quite different from those of our own solar system. Some statistical properties are summarized in Mazeh & Zucker (2002), Santos et al. (2003) and additional data may be obtained from .1 1 10 0 .2 .4 .6 .8 Distance (AU) Eccentricity Solar Extrasolar OGLE Figure 1. Eccentricity vs. distance for the extrasolar planets. For comparison the solar system planets and the two OGLE objects are also included. an example we display in Fig.1 the eccentricity versus mass distribution of all plants detected so far. While the planets close to the star (hot Jupiters) tend to have circular orbits due to tidal circular-ization the planets further out have a rather broad eccentricity distribution which is essentially indistinguishable from that of binary stars. Additionally , the cumulative eccentricity-period distribution of stellar binaries and planetary systems are also nearly identical for periods larger than about 10 days (Mazeh & Zucker 2002). This may imply a common origin of the eccentricities, caused for example by dynamical gravitational interaction. A summary of the main properties of the …