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Exoplanets

Gwenaël Boué, Isabelle Boisse
CAUP

The search for exoplanets began to achieve its first discovery around a solar-type star by the radial-velocity (RV) method in 1995. Seventeen years after, more than 700 exoplanets are known. These exoplanets reveal new physical and dynamical characteristics compared to the planets of the Solar system. From the theoretical point of view, these discoveries have led to extensive research on the formation, dynamical evolution, interior and atmospheric composition of the extrasolar planets. We will present this diversity in the third session of this advanced course.

Regarding the dynamical side, exoplanet systems show a reach variety of orbital configurations. Some of them have high eccentricities or high relative inclinations. Others are either very compact or more hierarchical. In order to understand their formation and evolution, during the first two sessions of this advanced course, we will see an overview of the dynamical behaviours of multiplanet systems.

As for the detection and the characterization of exoplanets, although RV, photometry and astrometry are extremely efficient techniques, they rely on indirect measurements. Phenomena modifying the surface of stars, such as pulsation, inhomogeneous convection, spots or magnetic cycles, might degrade parameters estimation. They can even prevent us from finding planets. Thus, exoplanetary surveys need to have a good knowledge of the planet-host stars and their magnetic activity. This will be presented in the last sessions.

Sessão 1: Planet-planet interaction I. Long-term evolution
5 junho 2012

Teacher: Gwenaël Boué
Level: graduate

At first order, planetary orbits in multiplanet systems are almost Keplerian. However,because of planet-planet interactions, the orbits are not fixed. They rotate slowly with time, and their eccentricities and inclinations oscillate with long periods. During this session, I will describe these motions and their consequencies for the formation of multiplanet systems and their long-term evolution.

Sessão 2: Planet-planet interaction II. Short-term evolution
22 junho 2012

Teacher: Gwenaël Boué
Level: graduate

In this second session, I will focus more on short-term interactions in multiplanet systems. These perturbations lead mainly to small deformations of planetary orbits. Nevertheless, if they are detectable, they can be used to infer the presence of an additional companion in a system with already one known planet. This is the basis of the Transit Timing Variation method that I will describe. As long as the perturbations are small, the orbital evolutions remain regular. We will see that if the interactions get stronger, multiplanet systems can become chaotic and unstable.

Sessão 3: Exoplanets: discoveries and statistical results
9 julho 2012

Teacher: Isabelle Boisse
Level: from undergraduate

After a brief introduction on the detection methods, I will give an overview of the diversity of the current discoveries, and highlight the main properties that could be sorted out from observations. I will also present theoretical studies that are stimulated from these. I will mainly focus on the RV results but I will also show the links between RV and other methods (transit, direct imaging and astrometry).

Sessão 4: Basic elements on activity and magnetism phenomena on solar-type stars
17 julho 2012

Teacher: Isabelle Boisse
Level: from undergraduate

In this course, I will give clues that I learned on the stellar activity and magnetism in relation to my research for detecting and characterizing exoplanets. I will then focus on solar-type stars and introduce the impact of magnetic field from their birth to the main sequence. I will present the dynamo theory explaining the magnetic field generation and how it is supposed to trigger the observed variability of the Sun and the stellar activity. I will thus give a short review of (solar and) stellar activities, how they are observed and characterized, their similitude and discrepancies that help to constrain the dynamo theory.