A close stellar companion influences the formation of planets in the system. The occurrence of stellar companions and characteristics of the stars and planets in the system provide constraints on the formation processes. We present results from our high-resolution Lucky Imaging survey for binary exoplanet host stars, including the discovery of stellar companion candidates to the transiting planet hosts WASP-12 and HAT-P-8.

Outward migration of planets due to Roche lobe overflow may play an important role in producing the presently observed distribution of planet parameters. We suggest that many of the currently known short period planets may have already migrated into the Roche distance from the star, and then deposited at their current semi-major axes by being migrated outwards due to angular momentum transfer from an episode of Roche lobe overflow (RLO). This RLO outward migration (RLOOM) could be sustained in the region where planetary radius increases with decreasing mass. We are modeling how RLOOM may leave what kind of planet parameter statistics. This modeling seeks to predict what observable signs of RLOOM there may be. Overflow of planetary mass may leave behind characteristic hot dust and gas as well as produce luminous signatures.

Due to the gravitational influence of density fluctuations driven by magneto-rotational instability in the gas disk, planetesimals and protoplanets undergo diffusive radial migration as well as changes of other orbital properties. The magnitude of the effect on particle orbits has important consequences for planet formation scenarios. We use the local-shearing-box approximation to simulate an ideal, isothermal, magnetized gas disk with vertical density stratification and simultaneously evolve numerous massless particles moving under the gravity of the gas and the host star. Although the results converge with resolution for fixed box dimensions, we find there exists no convergence of the response of the particles to the gravity of the gas against the horizontal box size, up to 16 disk scale heights. This lack of convergence indicate that caution should be exercised when interpreting local-shearing-box models involving gravitational physics of magneto-rotational turbulence.

Planetesimal formation occurs early in the evolution of a solar system, embedded in the circumstellar gas disk, and it is the crucial first step in planet formation. Their growth is difficult beyond boulder size, and likely proceeds via the accumulation of many rocks in turbulence followed by gravitational collapse - a process we are only beginning to understand. We have performed global simulations of the gas disk with embedded particles in the FLASH code. Particles and gas feel drag based on differential velocities and densities. Grains and boulders of various sizes have been investigated, from micron to km, with the goal of understanding where in the disk large planetesimals will tend to form, what sizes will result, and what size ranges of grains will be preferentially incorporated. We have so far simulated particles vertical settling and radial drift under the influence of gas drag, and their accumulations in turbulent clumps.

By making use of real information about the continental and oceanic surface distribution of the Earth, and cloudiness data from the International Satellite Cloud Climatology Project (ISCCP), we have studied the large-scale cloudiness behavior according to latitude and surface types (ice, water, vegetation and desert). These empirical relationships are used here to reconstruct the possible cloud distribution of historical epochs of the Earth history such as Late Cretaceous (90 My ago) and Late Triasic (230 My ago) when the landmass distribution was different. This information can be used to simulate the photometric variability of these planets according to their different geographical distribution.

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.

Planet-disk interaction predicts a change in the orbital elements of an embedded planet. Through linear and fully hydrodynamical studies it has been found that migration is typically directed inwards. Hence, this migration process gives natural explanation for the presence of the ’hot’ planets orbiting close to the parent star, and it plays a mayor role in explaining the formation of resonant planetary systems.

However, standard migration models for locally isothermal disks indicate a too rapid inward migration for small mass planets, and a large number of massive planets are found very far away from the star. Recent studies, including more complete disk physics, have opened up new paths to slow down or even reverse migration. The new findings on migration are discussed and connected to the observational properties of planetary systems.

Spectrographs like HARPS can now reach a sub-ms−1 precision in radial-velocity (RV) (Pepe & Lovis 2008). At this level of accuracy, we start to be confronted with stellar noise produced by 3 different physical phenomena: oscillations, granulation phenomena (granulation, meso- and super-granulation) and activity. On solar type stars, these 3 types of perturbation can induce ms−1 RV variation, but on different time scales: 3 to 15 minutes for oscillations, 15 minutes to 1.5 days for granulation phenomena and 10 to 50 days for activity. The high precision observational strategy used on HARPS, 1 measure per night of 15 minutes, on 10 consecutive days each month, is optimized, due to a long exposure time, to average out the noise coming from oscillations (Dumusque et al. 2011a) but not to reduce the noise coming from granulation and activity (Dumusque et al. 2011a and Dumusque et al. 2011b). The smallest planets found with this strategy (Mayor et al. 2009) seems to be at the limit of the actual observational strategy and not at the limit of the instrumental precision. To be able to find Earth mass planets in the habitable zone of solar-type stars (200 days for a K0 dwarf), new observational strategies, averaging out simultaneously all type of stellar noise, are required.

Gaia is an ESA Cornerstone mission, scheduled to be launched in spring 2013, dedicated to precisely measure the positions and motions of over a billion stars in our galaxy: the Milky Way. Gaia Data Processing Center Turin (DPCT), the Italian DPC, is hosted and operated at ALTEC in Turin. The primary objective of DPCT is to provide the infrastructure and operations support to the Astrometric Verification Unit (AVU) activities for CU3 and the Italian participation to the Gaia data processing tasks. DPCT will archive all of the data, produced for and delivered to DPAC as part of the Italian contribution to the activities of CU4, CU5, CU7, and CU8.

The direct detection of an extrasolar planet can provide accurate measurements of its orbit, mass and composition, greatly improving our understanding of how planets form and evolve. Recent advances in ground-based and space-based imaging techniques have now produced the first direct images of extrasolar planets. Typically these are many-Jupiter-mass planets on wide orbits. Direct imaging therefore probes the outer architecture of planetary systems and it is highly complementary to other techniques sensitive to inner architectures. This brief review summarizes the properties of the currently imaged exoplanets, provides an update on the orbit of Fomalhaut b, and highlights the emerging phenomenon of circumplanetary disks.

We present a mechanism for the formation of massive gas giants on wide orbits via disk fragmentation in the embedded phase of star formation. In this phase, protostellar disks undergo radial pulsations which lead to periodic disk compressions and formation of massive fragments on radial distances of the order of 50–300 AU. The fragments that form during the last episode of disk compression near the end of the embedded phase, when torque from spiral arms become weaker, may survive and mature into massive gas giants. This phenomenon can explain the existence of massive exoplanets on wide orbits is such systems as Fomalhaut and HR 8799.

We model the polarization in the system HD 189733 resulting from the planetary transit. This system has a short-period (2.2d) Jupiter-like planet with the radii ratio Rp/R* = 0.148, orbiting at the distance of 0.031 AU around the star.

We calculated the polarization of the system HD189733 to be 0.022% at the limb, which is consistent with the recent observational data. We suggest the shapes of the polarization parameters curves to be used for deriving the planet orbit inclination at the near limb transits as an alternative to standard transit method.

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 Exoplanet Roadmap Advisory Team (EPR-AT) was formed by the European Space Agency (ESA) to advise it on the best path for characterizing exoplanets including terrestrial planets. The EPR-AT delivered its report to ESA in August 2010. Here we summarize the findings of this task force.

Mean motion resonances are a common feature of both our own Solar System and of extrasolar planetary systems. Bodies can be trapped in resonance when their orbital semi-major axes change, for instance when they migrate through a protoplanetary disc. We use a Hamiltonian model to thoroughly investigate the capture behaviour for first and second order resonances. Using this method, all resonances of the same order can be described by one equation, with applications to specific resonances by appropriate scaling. We focus on the limit where one body is a massless test particle and the other a massive planet. We quantify how the the probability of capture into a resonance depends on the relative migration rate of the planet and particle, and the particle's eccentricity. Resonant capture fails for high migration rates, and has decreasing probability for higher eccentricities, although for certain migration rates, capture probability peaks at a finite eccentricity. We also calculate libration amplitudes and the offset of the libration centres for captured particles, and the change in eccentricity if capture does not occur. Libration amplitudes are higher for larger initial eccentricity. The model allows for a complete description of a particle's behaviour as it successively encounters several resonances. The model is applicable to many scenarios, including (i) Planet migration through gas discs trapping other planets or planetesimals in resonances; (ii) Planet migration through a debris disc; (iii) Dust migration through PR drag. The Hamiltonian model will allow quick interpretation of the resonant properties of extrasolar planets and Kuiper Belt Objects, and will allow synthetic images of debris disc structures to be quickly generated, which will be useful for predicting and interpreting disc images made with ALMA, Darwin/TPF or similar missions. Full details can be found in Mustill & Wyatt (2011).

The PLAnetary Transits and Oscillations of stars (PLATO) mission is in its definition study phase in the context of ESA's Cosmic Vision 2015-2025 program. PLATO is applying for a launch in 2017/18. Its goal is to detect transiting exoplanets, including terrestrial planets in the habitable zone, and to determine their basic parameters with unprecedented accuracy. In combination with the detailed analysis of the stellar parameters by astroseismology and with ground-based follow-up observations, this will allow characterizing the main properties of exoplanetary systems to a level not achieved before.

For the 451 stars of the HARPS high precision program, we study correlations between the radial-velocity (RV) variation and other parameters of the Cross Correlated Function (CCF). After a careful target selection, we found a very good correlation between the slope of the RV-activity index (log(R'HK)) correlation and the Teff for dwarf stars. This correlation allow us to correct RV from magnetic cycles given the activity index and the Teff.

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.

We calculate the simultaneous in situ formation of Jupiter and Saturn by the core instability mechanism considering the oligarchic growth regime for the accretion of planetesimals. We consider a density distribution for the size of planetesimals and planetesimals migration. The planets are immersed in a realistic protoplanetary disk that evolves with time. We find that, within the classical model of solar nebula, the isolated formation of Jupiter and Saturn undergoes significant change when it occurs simultaneously.