We present our current knowledge of the solar chemical composition based on the recent significant downward revision of the solar photospheric abundances of the most abundant metals very recently reviewed in detail by Asplund et al.  (2005a). These new solar abundances result from the use of a 3D hydrodynamical model of the solar atmosphere instead of the classical 1D hydrostatic models,accounting for departures from LTE, and improved atomic and molecular data. With these abundances, the new solar metallicity, Z, and Z/X, decrease to Z = 0.012 and Z/X = 0.0165 respectively, almost a factor of 2 lower than earlier widely used values. While resolving a number of longstanding problems, the new 3D-based solar photospheric composition also poses serious challenges for the standard solar model.

Hot massive stars are ideal indicators for present-day cosmic abundances. We review results from a non-LTE study of a larger sample of early B-type stars in the solar neighbourhood by Nieva & Przybilla (2012) and extend the analysis. Using comprehensive models with improved microphysics, novel analysis methodologies and high-quality spectra it is shown that the present-day chemical composition in massive stars out to several hundred parsec distance from the Sun is highly homogeneous. Abundances for about a dozen astrophysically important chemical elements are presented, including new preliminary data on aluminium, sulphur and argon. This establishes a cosmic abundance standard, which serves as a reference facilitating chemical peculiarities in other stars to be identified. Similarities and differences to the solar standard, and implications are discussed.

We examine static spherically symmetric polytropic spheres inPalatini f(R) gravity and show that no regular solutions to thefield equations exist for physically relevant cases such as amonatomic isentropic gas or a degenerate electron gas, thus castingdoubt on the validity of Palatini f(R) gravity as an alternative toGeneral Relativity.

Accurate and precise stellar ages are best determined for stars which are strongly observationally constrained, that is which are intrinsically oscillating. We review here the seismic diagnostics which are sensitive to stellar ages and provide some illustrating examples of seismically age-dated stars.

In dense molecular clouds, the birthplace of stars and planets, interstellar atoms andmolecules freeze onto extremely cold dust and ice particles. These ices are processed byultraviolet light and cosmic rays forming hundreds of far more complex species, some ofastrobiological interest. Eventually, these rain down on primordial planets where theytake part in the young chemistry on these new worlds.

Although the IR spectroscopy and energetic processing of interstellar ice analogs havebeen studied for nearly 30 years, similar studies of PAH containing ices have only justbegun. This paper presents recent results from laboratory studies on the vacuumultraviolet (VUV) photochemistry of PAHs in water ice at low temperatures to assess theroles they play in the photochemical evolution of interstellar ices and their relevance toastrobiology. A number of “surprises” were found in these studies on PAH containingwater-rich ices, indicating that PAHs likely play very important, unexpected roles incosmic ice chemistry, physics and astrobiology.

The rotation rate, level of magnetic activity and surface lithium abundance are age-dependent quantities in stars of about a solar mass and below. The physical reasons for the evolution of these phenomena are qualitatively understood, but accurate quantitative models remain dependent on empirical calibration using the Sun and stars of known age, chiefly in clusters. In this work I review the status of these “empirical age indicators”, outlining the astrophysics of their time dependence, describing the measurements, assessing the precision (and accuracy) of age estimates when applied to individual stars, and identifying their principle limitations in terms of the mass and age ranges over which they are useful. Finally, I discuss the “lithium depletion boundary” technique which, in contrast to the empirical methods, appears to provide robust, almost model-independent ages that are both precise and accurate, but which is only applicable to coeval groups of stars.

This paper provides an overview of wavefront sensing technologies. A brief background to the field of wavefront sensing is given, and several wavefront sensors are studied in detail. Particular attention is given to the Shack-Hartmann, Phase Diversity and Curvature wavefront sensors. Interferometric and Pyramid wavefront sensors are discussed as well as Schlieren imaging, algorithmic approaches (such as image sharpening), Shack-Hartmann Curvature hybrid wavefront sensing and modal wavefront sensors.

In this paper, I explore various transport processes that have a large impact of the distribution of elements inside stars and thus, on stellar evolution. A heuristic description of the physics behind equations is provided, and key references are given. Finally, for each process, I will briefly review (some) important results as well as discuss directions for future work.

The formalism of the simple model of galactic chemical evolution (GCE) and its main ingredients (stellar properties, initial mass function, star formation rate and gas flows) are presented in this tutorial. It is stressed that GCE is not (yet) an astrophysical theory, but it merely provides a framework in which the large body of data concerning the chemical composition of stars and gas in galaxies may be intrepreted. A few examples illustrating those concepts are provided, through studies of the Solar neighborhood and of the Milky Way's halo.

The current status of the DRIFT (Directional Recoil Identification From Tracks) experiment at Boulby Mine is presented, including the latest limits on the WIMP spin-dependent cross-section from 1.5 kg days of running with a mixture of CS2 and CF4. Planned upgrades to DRIFT IId are detailed, along with ongoing work towards DRIFT III, which aims to be the world’s first 10 m3-scale directional Dark Matter detector.

Star formation occurs in hierarchical patterns in both space and time. Galaxies form large regions on the scale of the interstellar Jeans length and these large regions apparently fragment into giant molecular clouds and cloud cores in a sequence of decreasing size and increasing density. Young stars follow this pattern, producing star complexes on the largest scales, OB associations on smaller scales, and so on down to star clusters and individual stars. Inside each scale and during the lifetime of the cloud on that scale, smaller regions come and go in a hierarchy of time. As a result, cluster positions are correlated with power law functions, and so are their ages. At the lowest level in the hierarchy, clusters are observed to form in pairs. For any hierarchy like this, the efficiency is automatically highest in the densest regions. This high efficiency promotes bound cluster formation. Also for any hierarchy, the mass function of the components is a power law with a slope of around − 2, as observed for clusters.

This lecture reviews current observational constraints on theoretical models of accretion-driven ejection in young stars. Fundamental properties of jets (collimation scale, kinematics, variability, density, composition) and ejection/accretion ratios are presented and compared at various stages of star formation (Class 0, I, II). Mass-loss rate derivations and evidence for a broader wind component around the jet are also critically examined.

This lecture reviews fundamental physical processes on star formation in galaxy interactions and mergers. Interactions and mergers often drive intense starbursts, but the link between interstellar gas physics, large scale interactions, and active star formation is complex and not fully understood yet. We show that two processes can drive starbursts: radial inflows of gas can fuel nuclear starbursts, triggered gas turbulence and fragmentation can drive more extended starbursts in massive star clusters with high fractions of dense gas. Both modes are certainly required to account for the observed properties of starbursting mergers. A particular consequence is that star formation scaling laws are not universal, but vary from quiescent disks to starbursting mergers. High-resolution hydrodynamic simulations are used to illustrate the lectures.

This paper describes the Heterodyne Instrument for the Far-Infrared (HIFI) to be launched onboard of ESA's Herschel Space Observatory, by 2008. The instrument is designed to be electronically tunable over a wide and continuous frequency range in the Far Infrared, with velocity resolutions better than 0.1 km s-1 and a high sensitivity. This will allow detailed investigations of a wide variety of astronomical sources, ranging from solar system objects, star formation regions to nuclei of galaxies. The instrument comprises 5 frequency bands covering 480–1150 GHz with SIS mixers and a sixth dual frequency band, for the 1410–1910 GHz range, with Hot Electron Bolometer Mixers (HEB). The Local Oscillator (LO) subsystem consists of a Ka-band synthesizer followed by 14 chains of frequency multipliers, 2 chains for each frequency band. A pair of Auto-Correlators and a pair of Acousto-Optic spectrometers process the two IF signals from the dual-polarization front-ends to provide instantaneous frequency coverage of 4 GHz, with a set of resolutions (140 kHz to 1 MHz), better than <0.1 km s-1. After a successful qualification program, the flight instrument entered the testing phase. We will also report on the first pre-flight test and calibration results together with the expected in-flight performance.


Total magnetic fields in spiral galaxies, as observed through their total synchrotronemission, are strongest (up to ≲30 µG) in the spiral arms. The degree of radio polarization is low; the field in the arms must be mostly turbulent or tangled. Polarized synchrotronemission shows that the resolved regular fields are generally strongest in the interarm regions (up to ≲15 µG), sometimes forming “magnetic arms” parallel to the optical arms. The field structure is spiral in almost every galaxy, even in flocculent and bright irregular types which lack spiralarms. The observed large-scale patterns of Faraday rotation in several massive spiral galaxies reveal coherent regular fields, as predicted by dynamo models. However, in most galaxies observed so far no simple patterns of Faraday rotation could be found. Either many dynamo modes are superimposed and cannot be resolved by present-day telescopes, or most of the apparently regular field is in fact anisotropic random, with frequent reversals, due to shearing and compressing gas flows. In galaxies with massive bars, the polarization pattern follows the gas flow. However, around strong shocks in bars, the compression of theregular field is much lower than that of the gas; the regular field decouples from the cold gas and is strong enough to affect the flow of the diffuse warm gas. – The average strength of the total magnetic field in the Milky Way is 6µG near the sun and increases to 20–40 μG in the Galactic center region.The Galactic field is mostly parallel to the plane, except in the center region. Rotation measure data from pulsars indicate several field reversals, unlike external galaxies, but some reversals could be due to distortions of thenearby field.

In this contribution I review the PAH-DIB hypothesis. Firstly, I list several propertiesof PAHs and their behaviour and expected signatures in space. Next, I give an overview ofthe current observational insights on the DIB carriers. I conclude with a briefdescription of recent results on the search for the DIB carriers and the prospects we havefor identification.

We review the basic equations describing the microscopic diffusion of elements in stars. We describe the two formalisms commonly used to describe a stellar plasma, i.e., the Chapman-Enskog method and the Burgers equations. We point out the underlying assumptions about the physical state of the plasma itself. We briefly describe the different approximations which are often used to solve these equations, and discuss their validity. One of the major problems lies in the calculation of the collision integrals, and we discuss the different approaches to solving these integrals, emphasizing on their domain of validity.

We outline the basic principles of scanning space astrometry, such as represented byHipparcos, Gaia, and some other astrometric satellites planned or proposed. We explain theneed for large-angle measurements, why these are essentially one-dimensional, how it ispossible to determine absolute parallaxes, and why a Hipparcos-type scanning law isfavourable. We discuss the choice of the basic angle between the two viewing directions,the principle of self-calibration, and why the resulting numerical problem must bedifficult to solve.

Several of the current and next-generation cosmic microwave background(CMB) experiments have polarimetric capability, promising to add tothe finesse of precision cosmology. One of the contaminating Galacticforegrounds is thermal emission by dust. Since optical interstellarpolarization is commonly seen, from differential extinction by alignedaspherical dust particles, it is expected that thermal emission fromthese grains will be polarized. Indeed, in the Galactic plane and indark (molecular) clouds, dust emission in the infrared andsubmillimetre has been measured to be polarized. It seems likely thatthe faint diffuse cirrus emission, of more relevance to CMBexperiments, will be polarized too. We discuss how well the amount ofpolarization of this component can be predicted, making use of what isknown about optical (and infrared and ultraviolet) interstellarpolarization and extinction. Some constraints on the alignment of thecarrier of the dust-correlated anomalous microwave emission can bemade as well.

Stars and star clusters form by gravoturbulent fragmentation of interstellar gas clouds. The supersonic turbulence ubiquitously observed in Galactic molecular gas generates strong density fluctuations with gravity taking over in the densest and most massive regions. Collapse sets in to build up stars.

Turbulence plays a dual role. On global scales it provides support, while at the same time it can promote local collapse. Stellar birth is thus intimately linked to the dynamical behavior of parental gas cloud, which governs when and where protostars form, and how they contract and grow in mass via accretion from the surrounding cloud material. The thermodynamic behavior of the star forming gas plays a crucial part in this process and influences the stellar mass function as well as the dynamic properties of the nascent stellar cluster.

This lecture provides a critical review of our current understanding of stellar birth and compares observational data with competing theoretical models.