We present a model for the dispersal of protoplanetary disks by winds from either the central star or the inner disk. These winds obliquely strike the flaring disk surface and strip away disk material by entraining it in an outward radial-moving flow at the disk-wind interface. This interface lies several disk scale heights above the mid plane. The disk dispersal time depends on the velocity at which disk material flows into the mixing layer. If this velocity is ~10% of the sound speed, the disk dispersal time at ~1–10 AU is ~5 Myr for a 0.01 M๏ disk around a solar mass star, with a spherical wind launched from the inner disk or central star with a typical mass loss rate of 10-8M๏yr-1 and terminal velocity of vw = 100 kms-1. We conclude that wind stripping is not a dominant disk dispersal mechanism compared with viscous accretion and photoevaporation. Nevertheless, wind stripping may affect the evolution of the intermediate disk regions.

The unexpected diversity of exoplanets includes a growing number of super Earth-planets, i.e. exoplanets with masses smaller than 10 Earth masses and a similar chemical and mineralogicalcomposition like Earth. We present a thermal evolution model for a super-Earth to calculate the sourcesand sinks of atmospheric carbon dioxide. The photosynthesis-sustaining habitable zone (pHZ) isdetermined by the limits of biological productivity on the planetary surface. We apply the model tocalculate the habitability of super-Earths in Gliese 581. The super-Earth Gl 581c is clearly outside thepHZ while Gl 581d at the outer edge of the pHZ could at least harbor some primitive life forms.

Adaptive Optics Systems are now routinely operated on several4 meter class telescopes, allowing to achieve angular resolutionsdown to 70 msec in the near-infrared. Although these Systems have excellentperformances, their use for exploring the physics and structureof AGN is still limited for the following reasons: the limiting magnitudeof the wavefront sensor is too high, the sensitivity of infrareddetectors does not give access to medium/high spectral resolution spectroscopyand the angular resolution achieved does not always fit theapparent size of the physical components responsible for emission featuresclose to the central engine. The new generation of 8 — 10 m classtelescopes bring improvements in this matter. However, some interestingresults have been obtained so far with Adonis, the ESO La Sillaadaptive optics System on the 3.60 meter telescope, in the investigationof AGN structure. In particular, a prominent structure has beendetected in the central arcsec core of NGC 1068, which might featurethe dusty/molecular torus expected on theoretical grounds.

The dynamics of stars and gas appear markedly different in flocculent, tidally induced and quasi-stationary spiral galaxies. Numerical simulations show that the gas and stars exhibit fairly chaotic dynamics during a tidal interaction, unlike the predictions of density wave theory. For a flocculent galaxy, the stars and gas tend to be situated in potential minima associated with the stellar distribution. I will demonstrate a possible observational test to distinguish between drivers of spiral structure by comparing the ages of stellar clusters, using the results of the simulations as an example.

With high resolution simulations, we are also starting to resolve giant molecular clouds, and can thus relate the properties of these clouds to the presence of spiral structure. Calculations so far suggest that spiral structure simply defines where the clouds form, rather than directly triggering star formation. In the last section of this review, I highlight recent efforts to produce synthetic HI and CO observations from numerical simulations.

Given the tendency of planets to form in multiples, and the observational evidence in support of the existence of potential planet-hosting stars in binaries or clusters, it is expected that extrasolar terrestrial planets are more likely to be found in multiple body systems. This paper discusses the prospects of the detection of terrestrial/habitable planets in multibody systems by presenting the results of a study of the long-term stability of these objects in systems with multiple giant planets (particularly those in eccentric and/or in mean-motion resonant orbits), systems with close-in Jupiter-like bodies, and systems of binary stars. The results of simulations show that while short-period terrestrial-class objects that are captured in near mean-motion resonances with migrating giant planets are potentially detectable via transit photometry or the measurement of the variations of the transit-timing due to their close-in Jovian-mass planetary companions, the prospect of the detection of habitable planets with the radial velocity technique is higher in systems with multiple giant planets outside the habitable zone and binary systems with moderately separated stellar companions.

Planet–star plasma interactions can be described as the interaction of a plasma flow with an obstacle, each being possibly magnetized. Examples of the 4 possible situations are found in our solar system, with intense radio emissions produced in 3 cases out of 4, when either the flow or the obstacle is strongly magnetized. Scaling laws are derived that relate the emitted radio power to the power dissipated in the various corresponding flow–obstacle interactions. They are generalized as a “radio–magnetic” scaling law between the output radio power and the magnetic energy flux convected onto the obstacle. Extrapolating it to the case of exoplanets, we find that hot Jupiters may produce very intense radio emissions due to planetary magnetospheric interaction with a strong stellar wind, reconnection between planetary and stellar magnetic fields, or unipolar interaction between the planet and a magnetic star (or strongly magnetized regions of the stellar surface). Emitted radio power is expected in the hecto–decameter range with intensity 103 to 106 times that of Jupiter (unless some “saturation” mechanism occurs). Corresponding flux densities should be detectable at tens of parsecs range with modern radio arrays. We briefly discuss ongoing observational searches as well as the interests of direct radio detection.

Among the various recombination schemes devised for nulling interferometry, one is to use the Achromatic Interfero Coronograph (AIC) which basically is a modified Michelson-Fourier interferometer made compact by cementing together optical components. The principle of this AIC is based on the focus-crossing property, from which a wave of light experiences an achromatic π phase shift when crossing a focus. Operated up to now only on a single telescope, this device is able to accomodate several beams for nulling. We describe the use of AIC as an interferometric nuller for a two-aperture interferometer.

Whereas the understanding of most phases of stellar evolution made considerable progress throughout the whole of the twentieth century, stellar formation remained rather enigmatic and poorly constrained by observations until about three decades ago, when major discoveries (e.g., that protostars are often associated with highly collimated jets) revolutionized the field. At this time, it became increasingly clearer that magnetic fields were playing a major role at all stages of stellar formation. 
We describe herein a quick overview of the main breakthroughs that observations and theoretical modelling yielded for our understanding of how stars (and their planetary systems) are formed and on how much these new worlds are shaped by the presence of magnetic fields, either those pervading the interstellar medium and threading molecular clouds or those produced through dynamo processes in the convective envelopes of protostars or in the accretion discs from which they feed.

To determine the star formation histories of dwarf galaxies we use fossil methods. Compared to the color-magnitude diagrams analyzes, which are well tested and widely accepted, the studies of integrated spectra are still young. In order to assess their capabilities and limitations, we compare the results of three publicly available star formation recovery programs (StarLight, STECKMAP and ULySS).

We present a tomographic reconstruction of polar plumes as observed in the Extreme Ultraviolet in January 2010. Plumes are elusive structures visible in polar coronal holes that may play an important role in the acceleration of the solar wind. However, despite numerous observations, little is irrefutably known about them. Because of line of sight effects, even their geometry is subject to debate. Are they genuine cylindrical features of the corona or are they only chance alignments along the line of sight? Tomography provides a means to reconstruct the volume of an optically thin object from a set of observations taken from different vantage points. In the case of the Sun, these are typically obtained by using a solar rotation worth of images, which limits the ability to reconstruct short lived structures. We present here a tomographic inversion of the solar corona obtained using only 6 days of data. This is achieved by using simultaneously three space telescopes (EUVI/STEREO and SWAP/PROBA2) in a very specific orbital configuration. The result is the shortest possible tomographic snapshot of polar plumes. The 3D reconstruction shows both quasi-cylindrical plumes and a network pattern that can mimic them by line of sight superimpositions. This suggests that the controversy on plume geometry is due to the coexistence of both types of structures.

The present work is placed in the framework of the preparation for the interpretation of the seismic space data from the space mission CoRoT. In this context, rotation have become one of the most limiting factors when analysing the observed spectra of stars. A general view on the effects of rotation on the oscillations is given from the point of view of a linear perturbation analysis. As well, the latest results about the effect of shellular rotation on adiabatic oscillation frequencies are addressed. Finally, the role of rotation on asteroseismic diagnostics is discussed. In particular, échélle diagrams and analysis of rotation profile variations are examined.

I discuss in this contribution constraints on the origin of mass-lossfrom young stars brought by recent observations at high angularresolution (0.1'' = 14 AU) of the inner regions ofwinds from T Tauri stars. Jet widths and collimation scales, the largeextent of the velocity profile as well as the detection of rotationsignatures agree with predictions from magneto-centrifugal disk windejection models. However dynamically cold disk wind solutions predicttoo large terminal velocities and too low jet densities and ionisationfractions, suggesting that thermal gradients (originating in anaccretion heated disk corona for example) may play an importantrole in accelerating the flow.

Numerical simulations have been carried out to assess theopportunity to detect extrasolar planets with MIRI: the mid-IRinstrument of NGST. Several coronagraphs and telescope designshave been investigated. As a result, we found that very youngplanets (50 Myr) as well as old planets (5 Gyr) can be imaged in thethermal-IR (5 μm to 20 μm) down to a few Jupiter masses ifan appropriate high-contrast coronagraph is in used. Promisingresults of numerical simulations are presented.

We review the literature of high dispersion studies of late B and early A type supergiants to assess the importance of non-LTE abundance calculations for them. Practically we are interested in learning which elements and species have such calculations been performed and then which of these should be implemented in calculations with plane-parallel LTE model atmospheres. The techniques available for the quantitative modeling of these atmospheres are outlined and some recent results are discussed.

A brief summary of some aspects of atomic physics theory useful for stellar atmospheres is given.

We give a review of cosmic ray propagation models. It is shown that the development of the theory of cosmic ray origin leads inevitably to the conclusion that cosmic ray propagation in the Galaxy is determined by effective particle scattering, which is described by spatial diffusion. The Galactic Disk is surrounded by an extended halo, in which cosmic rays are confined before escaping into intergalactic space. For a long time cosmic ray convective outflow from the Galaxy (galactic wind) was believed to be insignificant. However, investigations of hydrodynamic stability and an analysis of ISM dynamics (including cosmic rays) showed that a galactic wind was emanating near the disk, and accelerating towards the halo, reaching its maximum velocity far away from the disk. Therefore convective cosmic ray transport should be important in galactic halos. Recent analysis of the gamma-ray emissivity in the Galactic disk of EGRET data, which showed that cosmic rays are more or less uniformly distributed in the radial direction of the disk, as well as the interpretation of soft X-ray emission in galactic halos, give convincing evidence of the existence of a galactic wind in star forming galaxies.

We aim to improve the calculation of the Mg I line profiles in benchmark stars and to assess the impact of the new quantum mechanical calculations of inelastic collisions with hydrogen. The method is based on the non-Local Thermodynamic Equilibrium (NLTE) line formation using updated atomic data for a simple model atom of Mg I. Focus on the formation of the Mg I b triplet lines at 5167, 5172 and 5183 Å is presented for the Sun, Arcturus, HD 84937 (metal-poor dwarf) and HD 122563 (metal-poor giant). This study is preliminary and essentially tests the new atomic data. In this context, we show that NLTE effects are smaller for this triplet when quantum mechanical H collisions are included compared with the use of the semi-classical Drawin's formula.

The science case for FIR/Submm surveys of the extragalactic sky to be carried out from Dome C is reviewed. The main questions concerning the formation and evolution of galaxies making up the CIRB are outlined and opportunities to exploit Dome C unique observing conditions through single-dish observations are discussed.

We compare the merits of potential observatory sites on the Antarctic Plateau, in regard to the boundary layer, cloud cover, free atmosphere seeing, aurorae, airglow, and precipitable water vapour. We find that (a) all Antarctic sites are likely compromised for optical work by airglow and aurorae; (b) Dome A is the best existing site in almost all respects; (c) there is an even better site (“Ridge A”) 150 kms SW of Dome A; (d) Dome F is a remarkably good site except for aurorae; (e) Dome C probably has the least cloud cover of any of the sites, and might be able to use a predicted `OH hole' in the Spring.

The study of the oldest stellar populations in the Galaxy providesimportant cosmological information (e.g. a lower limit to the age ofthe Universe) and helps constraining models of galaxy formation. Themost commonly used stellar age indicators are reviewed and discussed,and the impact of GAIA on these topics is estimated.