Observations are inconsistent with a homogeneous and iso-tropic universe with ordinary matter and gravity. The universe is far from exact homogeneity and isotropy at late times, and the effect of the non-linear structures has to be quantified before concluding that new physics is needed. We explain how structure formation can lead to accelerated expansion, and discuss a semi-realistic model where the timescale in the change in the expansion rate emerges from the physics of structure formation.

Direct images of Betelgeuse were obtained over a span of 4 years with the Faint Object Camera on the Hubble Space Telescope. These images reveal the extended ultraviolet continuum emission (~2 times the optical diameter), the varying overall ultraviolet flux levels and a pattern of bright surface continuum features that change in position and appearance over several months or less. Concurrent photometry and radial velocity measures support the model of a pulsating star, first discovered in the ultraviolet from IUE. Spatially resolved HST spectroscopy reveals a larger extention in chromospheric emissions of Mg II as well as the rotation of the supergiant. Changing localized subsonic flows occur in the low chromosphere that can cover a substantial fraction of the stellar disk and may initiate the mass outflow.

Telescopes don’t make catalogues, they make intensity measurements; any preciseexperiment performed with a telescope ought to involve modelling those measurements.People make catalogues, but because a catalogue requires hard decisionsabout calibration and detection, no catalogue can contain all of the information in theraw pixels relevant to most scientific investigations. Here we advocate makingcatalogue-like data outputs that permit investigators to test hypotheses with almost thepower of the original image pixels. The key is to provide users approximations tolikelihood tests against the raw image pixels. We advocate three options, in order ofincreasing difficulty: The first is to define catalogue entries andassociated uncertainties such that the catalogue contains the parameters of an approximatedescription of the image-level likelihood function. The second is to produce aK-catalogue sampling in “catalogue space” that samplesa posterior probability distribution of catalogues given the data. The third is to exposea web service or equivalent that can compute the full image-level likelihood for anyuser-supplied catalogue.

Preliminary site testing datasets suggest that Dome C in Antarctica is one of the best sites on Earth for astronomical observations in the 200 to 500-μm regime, i.e. for far-infrared (FIR) and submillimetre (submm) astronomy. We present an overview of potential science cases that could be addressed with a large telescope facility at Dome C. This paper also includes a presentation of the current knowledge about the site characterics in terms of atmospheric transmission, stability, sky noise and polar constraints on telescopes. Current and future site testing campaigns are finally described.

The lack of radial velocity data in the Hipparcos catalogue was considered a significantdeficiency, so when Gaia was conceived, a spectrometer was a core constituent of itspayload. The Gaia Radial Velocity Spectrometer faced a number of design challenges, inparticular set by the need to balance kinematic and astrophysical capability. We presentan overview of the evolution of the instrument to its present form, identifying thecompeting technical, performance and programmatic factors which have shaped it.

A complete dedicated electronics, from front-end to back-end, was developed to instrument a MIMAC prototype. A front end ASIC able to monitor 64 strips of pixels and to provide their individual “Time Over Threshold” information has been designed. An associated acquisition electronics and a real time track reconstruction software have been developed to monitor a 512 channel prototype. This auto-triggered electronic uses embedded processing to reduce the data transfer to its useful part only, i.e. decoded coordinates of hit tracks and corresponding energy measurements. The electronic designs, acquisition software and the results obtained are presented.

This paper gives a description of some procedures to performnumerical simulations for coronagraphic instruments in realisticconditions.

Elements of kinematical and dynamical modeling of elliptical galaxies arepresented.In projection, NFW models resemble Sérsic models, but with a very narrow range of shapes (m = 3±1).The total density profile of ellipticals cannot be NFW-like because the predicted local M/L and aperture velocity dispersion within aneffective radius (Re) are much lower than observed. Stars must then dominate ellipticalsout to a few Re.Fitting an NFW model to the total density profile of Sérsic+NFW (stars+dark matter [DM]) ellipticals results in very high concentration parameters, asfoundby X-ray observers.Kinematical modeling of ellipticals assuming an isotropic NFW DM modelunderestimates M/L at the virial radius by a factor of 1.6 to 2.4, becausedissipationless ΛCDM halos have slightly different density profilesand slightly radial velocity anisotropy. In N-body+gas simulations of ellipticals as merger remnants ofspirals embedded in DM halos,the slope of the DM density profile is steeperwhen the initial spiral galaxies are gas-rich.The Hansen & Moore (2006)relation between anisotropy and the slope of the density profile breaks down for gas and DM, but the stars follow an analogous relation with slightly less radial anisotropies for a given density slope.Using kurtosis (h4) to infer anisotropy in ellipticals is dangerous, as h4 is also sensitive to small levels of rotation.The stationary Jeans equation provides accurate masses out to 8Re.The discrepancy between the modeling of Romanowsky et al. (2003),indicating a dearth of DM in ellipticals,and the simulations analyzed by Dekel et al. (2005), whichmatch thespectroscopic observations of ellipticals, is partly due to radial anisotropy and to observing oblate ellipticals face-on.However,one of the 15 solutions to the orbit modeling of Romanowsky et al. is found to have an amount andconcentration ofDMconsistent withΛCDM predictions.

AMBER is the General User near infrared focal instrument of the Very Large Telescope Interferometer. It is a single mode, dispersed fringes, three telescopes instrument. His limiting magnitude of the order of H=13 will allow him to tackle two dozens of extragalactic targets. His extremely high accuracy, in particular in phase closure and differential mode give good hope for very high dynamic range observation, possibly including hot extra solar planets. His relatively high spectral resolution will allow some stellar activity observations. Between this extreme goals, AMBER should have a wide range of applications including Young Stellar Objects, Evolved Stars, circumstellar material and many others. This papers tries to introduce AMBER to its future users and insists on what AMBER measures, how it calibrates it and how this could give the reader ideas for applications.

An analytical theory is developed that describes theprocess of nonlinear saturation of the magnetorotational instability. Thetheory employs the shearing sheet approximation with arbitrary (but linear)shear flow, and is asymptotically exact in a well-defined parameter regime. In this regime the instability saturates by extracting energy from the shear,and modifying the shear responsible for it. The saturation process requires both viscous and ohmic dissipation. The theory also describes the approach from small amplitude perturbations to the final strongly nonlinear saturated state.

The mass-loss mechanism in red supergiants is a long-stand-ing problem. The milliarcsecond angular resolution achieved by infrared long-baseline interferometry provides us with the only way to spatially resolve the region where the material is accelerated. For this goal, the 2.3 μm CO lines are important, because they form in the upper photosphere and the outer atmosphere (so-called MOLsphere). We present high-spatial and high-spectral resolution observations of the 2.3 μm CO lines in the red supergiants Betelgeuse and Antares using the Very Large Telescope Interferometer (VLTI). This has enabled us to spatially resolve the gas dynamics in the photosphere (and the MOLsphere) for the first time other than the Sun. We have detected vigorous motions of large CO gas clumps with velocities of up to 20–30 km s-1. Comparison of the CO line data taken 1 year apart shows a significant change in the dynamics of the atmosphere. In contrast to the CO line data, the continuum data reveal no or only marginal time variations. The observationally estimated gas density in the outer atmosphere at 1.3–1.4 R⋆ is higher than the values predicted by the current 3-D convection simulations by 6 to 11 orders of magnitude. Therefore, at the moment, convection alone cannot explain the detected vigorous gas motions in the extended outer atmosphere of Betelgeuse and Antares.

We describe a self-consistent spectrum analysis technique employing non-LTE line formation, which allows precise atmospheric parameters of massive stars to be derived: 1σ-uncertainties as low as  ~1% in effective temperature and  ~0.05–0.10 dex in surface gravity can be achieved. Special emphasis is given to the minimisation of the main sources of systematic errors in the atmospheric model computation, the observed spectra and the quantitative spectral analysis. Examples of applications are discussed for OB-type stars near the main sequence and their evolved progeny, the BA-type supergiants, covering masses of  ~8 to 25 M⊙ and a range in effective temperature from  ~8000 to 35000 K. Relaxing the assumption of local thermodynamic equilibrium in stellar spectral synthesis has been shown to be decisive for improving the accuracy of quantitative analyses. Despite the present examples, which concentrate on hot, massive stars, the same philosophy can be applied to line-formation calculations for all types of stars, including cooler objects like the Sun, once the underlying stellar atmospheric physics is reproduced consistently.

The emerging field of extrasolar planet search has shown an extraordinary ability to combine research by astrophysics, chemistry, biology and geophysics into a new and exciting interdisciplinary approach to understand our place in the universe. Are there other worlds like ours? How can we characterize those planets and assess if they are habitable? After a decade rich in giant exoplanet detections, observation techniques have now reached the ability to find planets of less than $10\,M_{\rm Earth}$ (so called Super-Earths) that may potentially be habitable. 
The detection and characterization of Earth-like planet is approaching rapidly with dedicated space observatories already in operation (Corot) or in development phase (Kepler, James Webb Space Telescope, Extremely Large Telescope (ELT), Darwin/TPF). Space missions like CoRoT (CNES, Rouan et al. 1998) and Kepler (NASA, Borucki et al. 1997) will give us statistics on the number, size, period and orbital distance of planets, extending to terrestrial planets on the lower mass range end as a first step, while missions like Darwin/TPF are designed to characterize their atmospheres. 
In this chapter we discuss how we can read a planet's spectral fingerprint and characterize if it is potentially habitable. We discuss the first steps to detect a habitable planet and set biomarker detection in context in Section 1. In Section 2 we focus on biomarkers, their signatures at different wavelengths, abiotic sources and cryptic photosynthesis – using Earth as our primary example – the only habitable planet we know of so far. Section 3 concentrates on planets around different stars, and Section 4 summarizes the chapter.

Galaxies in the Local Group span a factor of 15 in metallicity, ranging from the super-solar M 31 to the Wolf-Lundmark-Melotte (WLM) galaxy, which is the lowest-metallicity (0.1 Z⊙) Local Group galaxy currently forming stars. Studies of massive star populations across this broad range of environments have revealed important metal-licity-dependent evolutionary trends, allowing us to test the accuracy of stellar evolutionary tracks at these metallicities for the first time. The RSG population is particularly valuable as a key mass-losing phase of moderately massive stars and a source of core-collapse supernova progenitors. By reviewing recent work on the RSG populations in the Local Group, we are able to quantify limits on these stars’ effective temperatures and masses and probe the relationship between RSG mass loss behaviors and host environments. Extragalactic surveys of RSGs have also revealed several unusual RSGs that display signs of unusual spectral variability and dust production, traits that may potentially also correlate with the stars’ host environments. I will present some of the latest work that has advanced our understanding of RSGs in the Local Group, and consider the many new questions posed by our ever-evolving picture of these stars.

Despite recent progress, the first stages of cloud fragmentation andcore collapse remain poorly known. Significant observational advanceswere achieved in this field over the last decade, thanks to the use oflarge (sub)millimeter radiotelescopes such as the IRAM 30 m and theJCMT. Young protostars ("Class 0" objects), featuring powerful jetsand marked infall motions, were identified at the beginning of themain accretion phase. The density structure of numerous prestellarcondensations was also measured, setting strong constraints on theinitial conditions for individual collapse in molecular clouds. Morerecently, the advent of large-format bolometer arrays has allowedcomplete imaging of several nearby protoclusters in thesubmillimeter. The results suggest that stars are generally built fromfinite reservoirs of mass and imply that the stellar initial massfunction (IMF) is at least partly determined by turbulentfragmentation at the prestellar stage of star formation. This fieldwill greatly benefit from future large submillimeter projects such asFIRST/Herschel and ALMA in which Europe is involved at the highestlevel.

A general problem with the theory of stellar tides is that the observations indicate that the effectiveness in circularising binary orbits is much larger than predicted by current theories. A mechanism that may be at least part of the solution to this problem is resonance locking: prolonged enhanced tidal interaction when the tide is nearly resonant with a stellar oscillation mode. In these lectures we focus on the dynamical tide which takes into account that the tides can indeed excite non-radial oscillations in a star when the forcing period happens to be close to the period of a free oscillation mode of the star. Such resonant interaction can in principle speed-up the tidal evolution of a close binary. By including the Coriolis force in rotating stars the oscillation spectrum is enriched by rotational oscillation modes that can also be excited by the tides. Although the chances that the tides in a particular binary system happen to be close to a resonance with a free oscillation mode seem nevertheless slim, it appears that binary systems with a significant orbital eccentricity, and thus with several tidal harmonics, evolve through many resonances on timescales short compared to their main sequence (MS) lifetime. Stellar rotation, which is usually neglected in tidal calculations, plays an important role in that it is relatively easy to tidally spin a star up or down, whereby the forcing frequency (in the stellar frame) can move towards a resonance with a free oscillation mode of the star on relatively short timescales. Often this gives rise to resonance locking whereby the system remains nearly resonant, with enhanced tidal evolution, for a relatively long period. We will present the results of several numerical simulations, for both massive MS binaries and solar type binary systems in which resonance locking is studied in some detail.Note: in the following all numerically listed frequencies are normalised by the stellar break-up speed $\Omega_c=\sqrt{G\, M_s/R^3_s}$, unless explicitly indicated otherwise.

A large atmospheric field experiment STABLEDC (STudy of the Atmospheric Boundary Layer Environmental at Dome C plateau station) was held at the Franco-Italian station of Concordia at Dome C during 2004–2005. The aim of the field experiment was to study the processes occurring in the long-lived stable and the weak convective atmospheric boundary layers, observed during winter and summer respectively, and to collect the relevant parameters for the atmospheric models. We used both in situ and ground based remote sensing sensors to monitor the meteorological parameters. The thermal structure of the atmosphere and the diurnal behavior of the height of the atmospheric boundary layer, as seen by a minisodar, for a typical summer and winter day is shown. The behaviour of the surface temperature during the year evidences that, on average, the lowest surface temperatures occur in April and mid-August. Warming events were observed periodically during the winter with temperatures sometimes reaching the summer values. Average temperature profiles for each season are shown. During the winter the temperature strongly decreases in the first 100–200 m. However a detailed analysis of the potential temperature gradients evidence that generally the strongest gradients occur in a narrow layer of 10–40 m. Finally the potential to investigate the fine structure of the PBL with a high resolution minisodar, developed by ISAC/CNR, is discussed.

AMICA (Antarctic Multiband Infrared CAmera) is an instrument designed to perform astronomicalimaging in the near- (1-5 μm) andmid- (5–27 μm) infrared wavelength regions. Equipped with two detectors, an InSb 2562 and a Si:As 1282 IBC, cooled at 35 and 7 K respectively, it will be the first instrument to investigate the potential of the Italian-French base Concordia for IR astronomy. The main technical challenge is represented by the extreme conditions of Dome C (T ~ -90 °C, p ~ 640mbar). An environmental control system ensures the correct start-up, shut-down and housekeeping of the various components of the camera.AMICA will be mounted on the IRAIT telescope and will perform survey-mode observations in the Southern sky. The first task is to provide important site-quality data. Substantial contributions to the solution of fundamental astrophysical quests, such as those related to late phases of stellar evolution and to star formation processes, are also expected.

The space-borne missions CoRoT and Kepler have opened a new era in stellar physics, especially for evolved stars, with precise asteroseismic measurements that help determine precise stellar parameters and perform ensemble asteroseismology. This paper deals with the quality of the information that we can retrieve from the oscillations. It focusses on the conditions for obtaining the most accurate measurement of the radial and non-radial oscillation patterns. This accuracy is a prerequisite for making the best with asteroseismic data. From radial modes, we derive proxies of the stellar mass and radii with an unprecedented accuracy for field stars. For dozens of subgiants and thousands of red giants, the identification of mixed modes (corresponding to gravity waves propagating in the core coupled to pressure waves propagating in the envelope) indicates unambiguously their evolutionary status. As probes of the stellar core, these mixed modes also reveal the internal differential rotation and show the spinning down of the core rotation of stars ascending the red giant branch. A toy model of the coupling of waves constructing mixed modes is exposed, for illustrating many of their features.