Adaptive Optics (AO) will be essential for accomplishing many, if not most, of the science objectives currently planned for Extremely Large Telescopes including GMT, OWL, and TMT. AO will be needed to support a range of instrumentation, including near infrared (IR) imagers and spectrometers, mid IR imagers and spectrometers, “planet finding” instrumentation and wide-field optical spectrographs. Multiple advanced AO systems, utilizing the full range of concepts currently under development, will need to be combined into an integrated architecture to meet a broad range of requirements for field-of-view, spatial resolution and spectral bandpass.

In this paper, we describe several of the possible options for these systems and outline the range of issues, trade studies and component development activities which must be addressed. Some of these challenges include very high-order, large-stroke wavefront correction, tip-tilt sensing with faint natural guide stars to maximize sky coverage, laser guide star wavefront sensing on a very large aperture and achieving extremely high contrast ratios for the detection of extra-solar planet and other faint companions of nearby bright stars.

We discuss our numerical approach to the high-resolution modeling of the 3D structure and infrared emission of circumstellar dust disks. We examine the resonant structures of a dusty disk induced by the presence of giant planet, that outermost from a star. These features can serve as indicators of outermost planets embedded in the circumstellar dust disk and, moreover, can be used to determine its position, major orbital parameters and even the mass of the planet. Such planets are attractive goals for direct imaging. Our simulations indicate that Vega may have a massive planet $\sim$2 Jupiter mass at a distance ${>}50$ AU, and other giant planet(s) at a smaller distance, and Epsilon Eri may have a less massive planet $\sim$0.2 Jovian mass at a distance of 55–60 AU. Theoretical models and non-direct observations show that Beta Pictoris system can be a multiplanetary system with set of giant planets. Our dynamical model of the origin of the warping of the Beta Pictoris disk includes the gravitational influence of a planet with a mass of about 10 masses of Earth, at a distance of 70 AU, and a small inclination (2.5 deg) of the planetary orbit to the main dust disk. The direct signatures of this planet were discovered on 2002 by Keck observations.

The Spitzer Space Telescope (SST), aloft for over two years at time of writing, has so far devoted almost 600 hours of observing time to Solar System science, and small bodies make up a significant fraction of the objects that have been observed. For the first time we now have high accuracy mid-infrared data to study the fundamental mineralogical and physical properties of a large number of objects of different types. In this paper we review some of the exciting recent results derived from SST photometry (in six bands from 3.6 to 70 $\mu$m) and spectroscopy (from 5 to 40 $\mu$m) of asteroids and comets. The observations reveal their spectral energy distributions (SEDs), and we discuss three important science goals that can be addressed with these data: (1) finding compositional diagnostics of these objects, (2) determining their bulk thermal properties, and (3) understanding the surface evolution of primitive and icy bodies. We focus primarily on comet-asteroid transition objects, low-albedo asteroids, cometary nuclei, Trojans, Centaurs, and trans-Neptunian objects. In particular, we will show: emissivity features in the SEDs and identification of the compositional sources, the constraints on thermal inertia and infrared beaming through the samples of the thermal continuum, and an intercomparison of albedos across dynamically-related bodies.

We report on analysis of the poorly studied source 2RXP J130159.6-635806 at different epochs with ASCA, BeppoSAX, XMM-Newton and INTEGRAL. The source shows coherent X-ray pulsations at a period ${\sim}700$ s with $\dot{\nu}\sim 2\times 10^{-13}$ Hz s$^{-1}$. A broad band (1–60 keV) spectral analysis of 2RXP J130159.6-635806 based on almost simultaneous XMM-Newton and INTEGRAL data demonstrates that the source spectrum is an absorbed power law with a photon index $\Gamma\sim 0.5-1.0$ and a cut-off energy of ${\sim}25$ keV. We also report on the identification of the likely infrared counterpart to 2RXP J130159.6-635806. The interstellar reddening does not allow us to strongly constrain the spectral type of the counterpart. The latter is, however, consistent with a Be star, the kind of which is often observed in accretion powered X-ray pulsars.

Among the metal-poor dwarfs (Population II), a few are enriched in Nitrogen. Surprisingly, in spite of this peculiarity, their lithium abundance is similar to the Li abundance of the other dwarfs. Several scenarios of nitrogen enrichment are discussed, none is completely satisfactory, the most likely is a contamination by some very highly N-rich matter. But it could be speculated that these N-rich dwarfs may perhaps be stars escaped from N-rich globular clusters. An homogeneous analysis of this class of stars could be useful.

The rather low level of the lithium abundance in the old dwarfs, contrasting with the high level found in the Population I, requires a surprisingly large and rapid production of Li. Recent observations show in one Population I red giant, a very high lithium abundance. This observation, in agreement with some predictions of some theoretical models of giants and/or AGB stars is very encouraging.

I review current results from searching for galaxies giving rise to damped Ly$\alpha$ absorbers (DLAs) at $z<1$. Using 14 confirmed DLA galaxies, I further show that intermediate-redshift galaxies possess a large H I envelope out to $24-30\ h^{-1}$ kpc in radius. The photometric and spectral properties of these galaxies confirm that DLA galaxies are drawn from the typical field population, and not from a separate population of low surface brightness or dwarf galaxies. The spatial distribution of metals in the cold ISM of intermediate-redshift galaxies is characterised by a radial gradient of $-0.041\pm 0.012$ dex per kiloparsec (or equivalently a scale length of $10.6\ h^{-1}$ kpc) to $30\ h^{-1}$ kpc radius based on an ensemble of six galaxy-DLA pairs. Adopting this abundance gradient and known $N({\rm H I})$ profiles of nearby galaxies, I show that the observed low metal content of the DLA population can arise naturally as a combination of gas cross-section selection and metallicity gradients commonly observed in local disk galaxies.

Until recently hot cores were the first indirect manifestation of a young massive star, but recent observational successes are now providing us with the first candidates for the very early phases of massive star formation, probably the precursors of hot cores. The characteristic hot core chemistry is believed to arise from the evaporation of the icy mantles that accumulate on the dust grains during the collapse the leads to the formation of the massive star. The duration over which the grains are warmed is determined by the time taken for a pre-stellar core to evolve to the Main Sequence. Hence, hot cores and their precursors contain an integrated record of the physics and chemistry occurring during the collapse that led to the star. In this article I will review recent advances in the chemical modelling of hot cores and their precursors in light of the recent TPD experiments on a variety of ices and I will briefly discuss the implications of such studies for the interpretation of high mass protostellar objects.

The scope of this contribution is to review and discuss recent findings concerning the molecular environment of high-mass star forming regions. Special attention is devoted to “hot molecular cores” and their role in the formation of massive stars. After analysing the relationship between such cores and the surrounding molecular clumps, we discuss the results of interferometric observations of these objects and propose an evolutionary sequence proceeding from cold, pre-stellar cores to ultracompact HII regions.

This contribution describes a recent photometric survey of the Fornax dwarf spheroidal galaxy. CCD photometry in two colours (V and I) was obtained for a 10 degree$^2$ region centred on Fornax. By selecting stars sharing the colour-magnitude space of this system's RGB, we were able to remove the majority of field stars, and thereby probe the structure of Fornax at a previously unattained level. The data indicate that this dwarf galaxy contains two shells, both aligned with the Fornax major axis. Also, two ‘lobed’ structures sharing the alignment of these shells were discovered beyond the nominal tidal radius. These structures appear to be the remnant of a companion dwarf galaxy which merged with Fornax approximately 2 Gyr ago.

The most intensely discussed and controversial issue in time keeping has been the proposal before the International Telecommunications Union (ITU) to redefine Coordinated Universal Time (UTC) so as to replace leap seconds by leap hours. Should this proposal be adopted, the practice of inserting leap seconds would cease after a specific date. Should the Earth's rotation continue to de-accelerate at its historical rate, the next discontinuity in UTC would be an hour inserted several centuries from now. Advocates of this proposal cite the need to synchronize satellite and other systems, such as GPS, Galileo, and GLONASS, which did not exist and were not envisioned when the current system was adopted. They note that leap second insertions can be and have been incorrectly implemented or accounted for. Such errors have to date had localized impact, but they could cause serious mishaps involving loss of life. For example, some GPS receivers have been known to fail simply because there was no leap second after a long enough interval, other GPS receivers failed because the leap second information was broadcast more than three months in advance, and some commercial software used for internet time-transfer Network Time Protocol (NTP) could either discard all data received after a leap second or interpret it as a frequency change. The ambiguity associated with the extra second could also disrupt financial accounting and certain forms of encryption. Those opposed to the proposal question the need for a change, and also point out the costs of adjusting to the proposed change and its inconvenience to amateur astronomers and others who rely upon astronomical calculations published in advance. Reports have been circulated that the cost of checking and correcting software to accommodate the new definition of UTC would be many millions of dollars for some systems. In October 2005 American Astronomical Society asked the ITU for a year's time to study the issue. This commission has supported the efforts of the IAU's Committee on the Leap Second to make an informed recommendation, and anticipates considerable discussion at the IAU's 26th General Assembly in 2006.

We report on a survey of $^7$Li and $^6$Li isotopic abundances in metal-poor halo stars. The spectra of the 24 stars observed with VLT/UVES are of exceptionally high quality: $S/N>400$ and resolving power $R \simeq 120 000$. The $^7$Li abundances on our H$\alpha$$T_{\rm eff}$-scale show very small intrinsic scatter and a pronounced [Fe/H]-dependence. The resulting estimated primordial $^7$Li abundance is about 0.5 dex lower than predicted from Big Bang nucleosynthesis and the baryon density inferred by the cosmic microwave background. Nine of the stars yield a positive detection (${>}2\sigma$) of $^6$Li, which suggests the existence of a $^6$Li plateau for halo stars. The most interesting result is the presence of $^6$Li in the very metal-poor ([Fe/H]$=-2.74$) dwarf LP815-43 at the level of $^6$Li/$^7$Li${\simeq}\, 0.05\pm0.02$. According to models for stellar Li depletion due to diffusion or rotationally-induced mixing, a 0.5 dex $^7$Li depletion would require an unrealistic high initial $^6$Li abundance ($\log ^6{\rm Li} \ge 2.0$). Simultaneously, the observed high $^6$Li abundance at such low [Fe/H] can not be reconciled with existing models for Galactic cosmic ray spallation and $\alpha$-fusion reactions. This opens up exciting prospects of pre-Galactic $^6$Li production, possibly due to cosmological cosmic rays or late-decaying massive particles such as the gravitino or neutralino in the Big Bang.

I review recent progress in determining the rate coefficients appropriate to modelling interstellar chemistry, give some information on appropriate databases from which rate coefficients can be obtained, and point to the importance of the gas-grain interaction in determining molecular abundances. Although many of the fundamental gas-phase reactions have been studied in the laboratory, the failure of the models to explain the observations of water and methanol in cold clouds indicates that grains may have an important role, both in acting as a surface for freeze-out and in the synthesis of complex molecules. The major challenge in astrochemistry is to develop a more quantitative model for the role of grains and, in some cases, to incorporate a better, probably more complex, physical model for interstellar clouds.

This paper reviews the chemistry of star-forming regions, with an emphasis on the formation of high-mass stars. We first outline the basic molecular processes in dense clouds, their implementation in chemical models, and techniques to measure molecular abundances. Then, recent observational, theoretical and laboratory developments are reviewed on the subjects of hot molecular cores, cosmic-ray ionization, depletion and deuteration, and oxygen chemistry. The paper concludes with a summary of outstanding problems and future opportunities.

The present status of our knowledge of the composition of cometary nuclei is reviewed and compared with what we know on the composition of other Solar System minor bodies – interplanetary dust, meteorites, asteroids, trans-Neptunian objects. The current methods of investigations – by both in situ analysis and remote sensing – are described. Comets are active objects pouring their internal material to form a dusty atmosphere which can be investigated by remote sensing. This is not the case for minor planets and trans-Neptunian objects for which only the outer surface is accessible. Collected interplanetary dust particles and meteorites can be analysed at leisure in terrestrial laboratories, but we do not know for certain which are their parent bodies.

Considerable progresses have been made from spectroscopic observations of active comets, mainly at infrared and radio wavelengths. We probably know now most of the main components of cometary ices, but we still have a very partial view of the minor ones. The elemental composition of cometary dust particles is known from in situ investigations, but their chemical nature is only known for species like silicates which have observable spectral features. A crucial component, still ill-characterized, is the (semi-)refractory organic material of high molecular mass present in grains. This component is possibly responsible for distributed sources of molecules in the coma. A large diversity of composition from comet to comet is observed, so that no “typical comet” can be defined. No clear correlation between the composition and the region of formation of the comets and their subsequent dynamical history can yet be established.

Over the coming two decades astronomers will plan, construct and exploit extremely large telescopes operating at both optical (ELTs) and radio (SKA) wavelengths. In studies of galaxy evolution and cosmology the combination of the two types of facility are likely to be extremely powerful. In this paper I will review the key questions that the ELT/SKA combination seem set to solve, focussing on the unique advantages afforded by optical and radio observations against the backdrop of the other theoretical and observational information to be available by 2020.

Using integral field spectroscopy (IFS) we have observed QSOs which were previously known to have intervening DLAs, to search for emission lines in the field surrounding the QSOs. The sample consists of 13 DLAs plus 7 sub-DLAs at $z>2$, from which we find emission line candidates at the expected wavelengths for 8 systems, implying a detection frequency of 40%. Emission lines detected at the DLA redshifts are interpreted as being due to Ly$\alpha$ lines from galaxies associated with the DLA clouds. Candidates are detected at $3-4\sigma$ levels in both narrow-band images and spectra created from the data cubes. We find no preference for candidate detection associated with either high or low metallicity DLAs. In comparison with the properties of previously known DLA galaxies, the candidates show similar distributions of line fluxes and line widths, but their impact parameters are slightly different, suggesting H I cross sections larger than 10 kpc.

We present the results of near-infrared imaging of the dwarf spheroidal galaxies Fornax and Leo I as part of a photometric survey of stellar populations in Local Group dwarf galaxies. Wide-field observations in the J, H, and $K_s$ bands have been obtained with the SOFI camera at the ESO NTT at La Silla, Chile. The aim of this project is to study the evolution of Local Group dwarf spheroidal galaxies, with special regard to star formation at intermediate epochs. The near-infrared data, together with optical catalogs from the Padova Local Group wide-field survey, provide a very large color baseline ideal to study the properties of red giant branch (RGB) and asymptotic giant branch (AGB) stars.

Very massive stars (${\gtrsim} 20$ M$_{\odot}$) are rare but important components of galaxies. Products of core nucleosynthesis from these stars are distributed into the circumstellar environment via wind-driven mass loss. Explosive nucleosynthesis after core collapse further enriches the galactic medium. Clusters of such stars can produce galactic chimneys which can pierce the galactic disk and chemically enrich intergalactic space. Such processes are vitally important to the chemical evolution of the early Universe, when the stellar mass function was much more weighted to massive stars.

Very massive stars are difficult to study, since they are formed in distant clusters which yield problems of sensitivity and source crowding. A relatively new tool for studying these systems is via high spatial, spectral and temporal resolution observations in the X-ray band. In this note we describe some recent progress in studying mechanisms by which very massive stars produce X-ray emission.

The working group “The Future Development of Ground-Based Astrometry” of the IAU Division 1, founded in 2000, continued its activity for the last triennium. Part of its results—meetings or programs—are presented here. The FDGBA web site is http://www.astro.ro/wg

We discuss the preliminary results of a survey of young ($<$300 Myr), close ($<$50 pc) stars with the Simultaneous Differential Extrasolar Planet Imager (SDI) implemented at the VLT and the MMT. SDI uses a quad filter to take images simultaneously at 3 wavelengths surrounding the 1.62 $\mu$m methane bandhead found in the spectrum of cool brown dwarfs and gas giants. By performing a difference of images in these filters, speckle noise from the primary can be significantly attenuated, resulting in photon noise limited data. In our survey data, we achieved H band contrasts $>$25000 (5$\sigma \Delta$F1(1.575$\mu$m)$>$10 mag, $\Delta$H$>$11.5 mag for a T6 spectral type) at a separation of 0.5” from the primary star. With this degree of attenuation, we should be able to image (5$\sigma$ detection) a 2-4 Jupiter mass planet at 5 AU around a 30 Myr star at 10 pc. We are currently completing our survey of young, nearby stars, with complete datasets for 35 stars in the southern sky (VLT) and 7 stars in the northern sky (MMT). We believe that our SDI images are the highest contrast astronomical images ever made from ground or space for methane rich companions.