Planetary satellites are an integral part of the hierarchy of planetary systems. Here we make two predictions concerning their formation. First, primordial satellites, which have an array of distinguishing characteristics, form only around giant planets. If true, the size and duration of a planetary system's protostellar nebula, as well as the location of its snow line, can be constrained by knowing which of its planets possess primordial satellites and which do not. Second, all satellites around terrestrial planets form by impacts. If true, this greatly enhances the constraints that can be placed on the history of terrestrial planets by their satellites' compositions, sizes, and dynamics.

We analyze the statistics of Doppler-detected planets and Keplere-detected planet candidates of high integrity. We determine the number of planets per star as a function of planet mass, radius, and orbital period, and the occurrence of planets as a function of stellar mass. We consider only orbital periods less than 50 days around Solar-type (GK) stars, for which both Doppler and Kepler offer good completeness. We account for observational detection effects to determine the actual number of planets per star. From Doppler-detected planets discovered in a survey of 166 nearby G and K main sequence stars we find a planet occurrence of 15+5−4% for planets with M sin i = 3–30 ME and P < 50 d, as described in Howard et al. (2010). From Keplere, the planet occurrence is 0.130 ± 0.008, 0.023 ± 0.003, and 0.013 ± 0.002 planets per star for planets with radii 2–4, 4–8, and 8–32 RE, consistent with Doppler-detected planets. From Keplere, the number of planets per star as a function of planet radius is given by a power law, df/dlog R = kRRα with kR = 2.9+0.5−0.4, α = −1.92 ± 0.11, and R = RP/RE. Neither the Doppler-detected planets nor the Keplere-detected planets exhibit a “desert” at super-Earth and Neptune sizes for close-in orbits, as suggested by some planet population synthesis models. The distribution of planets with orbital period, P, shows a gentle increase in occurrence with orbital period in the range 2–50 d. The occurrence of small, 2–4 RE planets increases with decreasing stellar mass, with seven times more planets around low mass dwarfs (3600–4100 K) than around massive stars (6600–7100 K).

In order to understand general planet characteristics and constrain formation models it is necessary to scan over the widest possible parameter range of discovered systems. Due to detection biases, the domain of very-low mass planets had remained poorly explored. Only with improving measurement precision it has been possible to enter in the sub-Neptune mass range. The HARPS planet search program has been particularly efficient in detecting such ice giants and super earths. The present talk will summarize the obtained results and the characteristics of the low-mass population of exoplanets.

Theoretical studies suggest that C/O and Mg/Si are the most important elemental ratios in determining the mineralogy of terrestrial planets. The C/O ratio controls the distribution of Si among carbide and oxide species, while Mg/Si gives information about the silicate mineralogy. We find mineralogical ratios quite different from those of the Sun, showing that there is a wide variety of planetary systems which are not similar to Solar System. Many of planetary host stars present a Mg/Si value lower than 1, so their planets will have a high Si content to form species such as MgSiO3. This type of composition can have important implications for planetary processes like plate tectonics, atmospheric composition or volcanism. Moreover, the information given by these ratios can guide us in the search of stars more probable to form terrestrial planets.

Studying the internal structure of exoplanet-host stars compared to that of similar stars without detected planets is particularly important for the understanding of planetary formation. In this framework, asteroseismic studies represent an excellent tool for a better characterization of stars and for a precise determination of the stellar parameters like mass, radius, gravity, effective temperature. The detection of stellar oscillations is obtained with the same instruments as used for the discovery of exoplanets, both from the ground and from space, although the time scales are very different. Here I discuss some details about the characterization of exoplanethost stars from seismology and the importance of the helium and heavy element abundances in this respect.

During the first 33.5 days of science-mode operation of the Kepler Mission, the stellar flux of 156,000 stars were observed continuously. The data show the presence of more than 1800 eclipsing binary stars, over 700 stars with planetary candidates, and variable stars of amazing variety. Analyses of the commissioning data also show transits, occultations and light emitted from the known exoplanet HAT-P7b. The depth of the occultation is similar in amplitude to that expected from a transiting Earth-size planet and demonstrates that the Mission has the precision necessary to detect such planets. On 15 June 2010, the Kepler Mission released most of the data from the first quarter of observations. At the time of this data release, 706 stars from this first data set have exoplanet candidates with sizes from as small as that of the Earth to larger than that of Jupiter. More than half the candidates on the released list have radii less than half that of Jupiter. Five candidates are present in and near the habitable zone; two near super-Earth size, one similar in size to Neptune, and two bracketing the size of Jupiter. The released data also include five possible multi-planet systems. One of these has two Neptune-size (2.3 and 2.5 Earth-radius) candidates with near-resonant periods as well as a super-Earth-size planet in a very short period orbit.

The CoRoT space telescope is detecting planets with the transit method for more than four years. Its tally includes hot jupiter planets with orbital periods up to 95 days but also the first Super-Earth, CoRoT-7b, whose density is similar to the Earth's one, as well as close-in brown dwarfs. We review the status of the CoRoT/Exoplanet program, including some elements of the multi step strategy of complementary observations. We then present some of the CoRoT exoplanetary systems and how they widen the range of properties of the close-in low mass population and contribute to our understanding of the properties of planets.

Theories of planet formation predict the birth of giant planets in the inner, dense, and gas-rich regions of the circumstellar disks around young stars. These are the regions from which strong CO emission is expected. Observations have so far been unable to confirm the presence of planets caught in formation. We have developed a novel method to detect a giant planet still embedded in a circumstellar disk by the distortions of the CO molecular line profiles emerging from the protoplanetary disk's surface. The method is based on the fact that a giant planet significantly perturbs the gas velocity flow in addition to distorting the disk surface density. We have calculated the emerging molecular line profiles by combining hydrodynamical models with semianalytic radiative transfer calculations. Our results have shown that a giant Jupiter-like planet can be detected using contemporary or future high-resolution near-IR spectrographs such as VLT/CRIRES or ELT/METIS. We have also studied the effects of binarity on disk perturbations. The most interesting results have been found for eccentric circumprimary disks in mid-separation binaries, for which the disk eccentricity - detectable from the asymmetric line profiles - arises from the gravitational effects of the companion star. Our detailed simulations shed new light on how to constrain the disk kinematical state as well as its eccentricity profile. Recent findings by independent groups have shown that core-accretion is severely affected by disk eccentricity, hence detection of an eccentric protoplanetary disk in a young binary system would further constrain planet formation theories.

Main sequence stars are commonly surrounded by disks of dust. From lifetime arguments, it is inferred that the dust particles are not primordial but originate from the collision of planetesimals, similar to the asteroids, comets and KBOs in our Solar system. The presence of these debris disks around stars with a wide range of masses, luminosities, and metallicities, with and without binary companions, is evidence that planetesimal formation is a robust process that can take place under a wide range of conditions. Debris disks can help us learn about the formation, evolution and diversity of planetary systems.

The β Pic disk of dust and gas has been regarded as the prototype of young planetary systems since the 1980s and has revealed over the years an impressive amount of indirect signs pointing toward the presence of at least one giant planet. We present here the recently detected first giant planet around this star. We show how this planet could explain some very peculiar features of the star environment (disk, spectroscopic variability), and how it constrains the scenarios of planetary system formation (timescales, mechanisms).

We discuss the effects of close scattering and merging between planets on distributions of mass, semimajor axis and orbital eccentricity, using population synthesis model of planet formation, focusing on the distributions of close-in super-Earths, which are being observed recently. We found that a group of compact embryos emerge interior to the ice line, grow, migrate, and congregate into closely-packed convoys which stall in the proximity of their host stars. After the disk-gas depletion, they undergo orbit crossing, close scattering, and giant impacts to form multiple rocky Earths or super-Earths in non-resonant orbits around ~ 0.1AU with moderate eccentricities of ~ 0.01–0.1. The formation of these planets does not depend on model parameters such as type I migration speed. The fraction of solar-type stars with these super-Earths is anti-correlated with the fraction of stars with gas giants. The newly predicted family of close-in super-Earths makes less clear “planet desert” at intermediate mass range than our previous prediction.

Previous models of the combined growth and migration of protoplanets needed large ad hoc reduction factors for the type I migration rate as found in the isothermal approximation. In order to eliminate these factors, a simple semi-analytical model is presented that incorporates recent results on the migration of low mass planets in non-isothermal disks. It allows for outward migration. The model is used to conduct planetary populations synthesis calculations. Two points with zero torque are found in the disks. Planets migrate both in- and outward towards these convergence zones. They could be important for accelerating planetary growth by concentrating matter in one point. We also find that the updated type I migration models allow the formation of both close-in low mass planets, but also of giant planets at large semimajor axes. The problem of too rapid migration is significantly mitigated.

Masses and radii are the primary observables to characterize exoplanets today. A self-consistent theoretical approach is presented that allows to calculate mass- and radius-distributions of exoplanet populations from basic physical principles and avoids the usual parametrisation of a multitude of processes.

The eccentric orbits of the known extrasolar giant planets provide evidence that most planet-forming environments undergo violent dynamical instabilities. Here, we numerically simulate the impact of giant planet instabilities on planetary systems as a whole. We find that populations of inner rocky and outer icy bodies are both shaped by the giant planet dynamics and are naturally correlated. Strong instabilities – those with very eccentric surviving giant planets – completely clear out their inner and outer regions. In contrast, systems with stable or low-mass giant planets form terrestrial planets in their inner regions and outer icy bodies produce dust that is observable as debris disks at mid-infrared wavelengths. Fifteen to twenty percent of old stars are observed to have bright debris disks (at λ ~ 70μm) and we predict that these signpost dynamically calm environments that should contain terrestrial planets.

We present high resolution computer simulations of dust dynamics and planetesimal formation in turbulence triggered by the magnetorotational instability. Particles representing approximately meter-sized boulders clump in large scale overpressure regions in the simulation box. These overdensities readily contract due to the combined gravity of the particles to form gravitationally bound clusters with masses ranging from a few to several ten times the mass of the dwarf planet Ceres. Gravitationally bound clumps are observed to collide and merge at both moderate and high resolution. The collisional products form the top end of a distribution of planetesimal masses ranging from less than one Ceres mass to 35 Ceres masses. It remains uncertain whether collisions are driven by dynamical friction or underresolution of clumps.

The two current models for giant planet formation are core accretion and disk instability. We discuss the core masses and overall planetary enrichment in heavy elements predicted by the two formation models, and show that both models could lead to a large range of final compositions. For example, both can form giant planets with nearly stellar compositions. However, low-mass giant planets, enriched in heavy elements compared to their host stars, are more easily explained by the core accretion model. The final structure of the planets, i.e., the distribution of heavy elements, is not firmly constrained in either formation model.

The standard picture of planet formation posits that giant gas planets are over-grown rocky planets massive enough to attract enormous gas atmospheres. It has been shown recently that the opposite point of view is physically plausible: the rocky terrestrial planets are former giant planet embryos dried of their gas “to the bone” by the influences of the parent star. Here we provide a brief overview of this “Tidal Downsizing” hypothesis in the context of the Solar System structure.

Brown dwarfs and massive planets have similar structures, and there is probably an overlap in mass between the most massive planets and the lowest mass brown dwarfs. This raises questions as to what extent the structures of the most massive planets and lowest mass brown dwarfs differ, and what similarities (or not) there might be between their formation mechanisms. Here I discuss these issues on the background of recent numerical simulations of star formation, new evidence from cosmochemistry about the conditions in the early solar system, and recently discovered mechanisms that can expedite planetesimal and possibly planet formation greatly.

Recent direct imaging discoveries of exoplanets have raised new questions about the formation of very low-mass objects in very wide orbits. Several explanations have been proposed, but all of them run into some difficulties, trying to explain all the properties of these objects at once. Here we present the results of a deep adaptive optics imaging survey of 85 stars in the Upper Scorpius young association with Gemini, reaching contrasts of up to 10 magnitudes. In addition to identifying numerous stellar binaries and a few triples, we also found several interesting sub-stellar companions. We discuss the implications of these discoveries, including the possibility of a second pathway to giant planet formation.

Brown dwarfs are intermediate objects between planets and stars. The lower end of the brown-dwarf mass range overlaps with the one of massive planets and therefore the distinction between planets and brown-dwarf companions may require to trace the individual formation process. We present results on new potential brown-dwarf companions of Sun-like stars, which were discovered using CORALIE radial-velocity measurements. By combining the spectroscopic orbits and Hipparcos astrometric measurements, we have determined the orbit inclinations and therefore the companion masses for many of these systems. This has revealed a mass range between 25 and 45 Jupiter masses almost void of objects, suggesting a possible dividing line between massive planets and sub-stellar companions.