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IMPORTANTE : Este documento não pôde ser incluído no projeto apresentado ao CNPq porque o programa usado, por razoes desconhecidas, expandia o seu conteúdo para mais de 16 MB. No projeto apresentado consta apenas o texto. O projeto que está aqui é o completo. TITULO: PARTICIPAÇÃO EM 3 REUNIÕES CIENTÍFICAS INTERNACIONAIS DE 22/08/2005 A 17/09/2005. Aconfirmação de registro e aceitação do trabalho nas reuniões CELMEC IV e 10 anos de 51 Peg já está registrada nas páginas dos eventos. Os prazos da reunião DPS ainda estão abertas. As confirmações de registro e inscrição deverão estar na Internet a partir da metade de Julho. Os endereções são: http://www.obs-hp.fr/~51peg10y/#List_of_participants http://www.mat.uniroma2.it/celmec/abstracts4.htm http://www.dps2005.com (seguir os links) ANEXO I (1) CELMEC IV - 4th International meeting on Celestial Mechanics (Principal reunião européia de Mecänica Celeste) Participação como Palestrante e Editor dos Proceedings. Palestra: EXOPLANETARY SYSTEMS S. Ferraz-Mello Introduction The new astronomical instruments of the past decades were responsible for a deep renewal in Celestial Mechanics. Thousands of asteroids (including many inr resonance, Trojans, NEOS,…), tens of new planetary satellites, the Kuiper belt objects and, now, more than one hundred new planetary systems, reshaped the field by the addition of an enormous bunch of new problems. This lecture deals with the new problems that were brought to Celestial Mechanics by the newly discovered extrasolar planets. The central problems are related to the origin and stability of the new systems. Astronomers have to explain why many of the found planets are so large. There is a known selection effect in the observations favoring the discovery of largest objects in small orbits (see fig.1). But among the large objects being discovered, some are too large. We remind that accepted theories, before the discovery of the exoplanets, were stating that 1 Jupiter mass was more or less the upper limit for the size of one planet (see the discussion in Artymowicz et al. 1997). Migration We have to explain the proximity of many discovered planets to the central stars and the great deal of very eccentric orbits found (fig. 2). The answer is “migration”. But the migration processes that may have affected the Solar System some Gyrs ago, is far from being capable of driving planets from some AU from the central star to its very neighborhood and of increasing their eccentricities to the known values. ![]() Fig.1 - Distribution of the discovered exoplanets. Crosses show those discovered by photometry (transits) and the other symbols those discovered by radial velocity measurements. (Gray circles are discoveries done before June 1999, open squares are discoveries done after May 2003 and triangles are discoveries done between 1999 and 2003.) Solid lines: half-amplitudes of variation of the stellar radial velocity due to the exoplanets (updated December 2004). ![]() Fig. 2 - Distribution of the orbital elements of the discovered exoplanets. The understanding of these problems comes from the use of hydrodynamical codes allowing a better knowledge of the processes inside the disk where the planets did form and the evaluation of the forces and torques acting on them due to the interaction between disk and planet (see Papaloizou, 2003). The disk-planet interaction transfer energy and angular momentum to the planet orbit has been shown to be very efficient. If the remnants of the protoplanetary disk are outside the orbit of the planet, the result is that the planetary orbit spirals inward and becomes increasingly eccentric. This process will last while there is enough matter in the disk close to the planetary orbit. The next step is a very well-know process in Celestial Mechanics. If there is a second planet moving in an orbit interior to the orbit of the planet being pushed by the cloud, sooner or later, their periods will become commensurable and a capture in resonance may occur. The probability of capture will depend on several factors: (i) the order q of the commensurability (p+q):p of the periods (the probability of capture is significant only for small values of q); (ii) the adiabaticity of the process (a capture may only occur if the contraction of the orbit is enough slow); (iii) the eccentricity of the orbits (the probability of capture vanishes if the eccentricities are large) (see Gomes, 1995). In case of non capture, the most probable issue is a catastrophic approach of the two planets with unpredictable consequences. It is interesting to see that in all known cases (but one) of extrasolar planets around Main Sequence stars in which the period ratio is smaller than 3, the planets are tied by a mean-motion resonance (Table I). TABLE I – Extrasolar planets with period ratio < 3
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