We review the recent progress in the exploration of the interrelations between primitive small bodies of the solar system which are preserved the pristine material in their interior: cometary nuclei, Transneptunian Objects, Centaurs, and primitive asteroids, and they are considered as primordial objects. In addition, we discuss the properties of the asteroid-comet transition objects which have really enigmatic behavior. The comets have most primitive, accessible material in the solar system but we do not know what is hidden below the evolved surface layers. Comets must become dormant but we do not know whether the ice is exhausted or sublimation is inhibited (blocked by quenching mechanisms). There must be many dormant comets masquerading as asteroids but we do not know to identify these bodies unless via serendipitous discovery observations. Indeed, there are some asteroids which temporarily show comet-like activity. These are among the Damocloids (C/2001 OG108 (LONEOS)), main belt asteroids (7968 Elst-Pizarro = 133P/E-P) and Near-Earth objects (4015 Wilson-Harrington = 107P/W-H). The important questions are: where is the pristine material in the cometary nuclei and in the asteroid-comet transition objects, do comets lose their ice or seal it in? Both the large survey projects and in-situ space missions will help to answer these questions in the near future.

This triennial report from Commission 8 covers astrometry-related matters for objects ranging from Solar system bodies out to Milky Way stars and QSOs at cosmological distances. This enormous range of distances is needed to establish, maintain, and improve the metric of the visible Universe--a very challenging effort since everything is moving. The progress of astrometry in the last three years (2002-2005) is reflected here. To locate the references, the reader is advised to check the NASA ADS Astronomy Abstract Service and the expanded report posted at URL http://www.pha.jhu.edu/iau_comm8/comm8.html

We present results of a photometric survey for carbon stars in the M31 dwarf spheroidal galaxies. From the low frequency of carbon stars in these galaxies compared to their Milky Way cousins we conclude that they consist of predominantly ancient stellar populations. However, the complexity and variety of the metallicity distributions in the M31 dwarf spheroidals suggest that they still experienced an extended epoch of star formation.

It is discovered that young SNRs have very thin filaments emitting nonthermal X-rays from accelerated electrons. In this paper, a new age and distance indicator is proposed using the spectral and spatial features of nonthermal filaments. We applied this method to the Vela Jr. SNR, for which age and distance are still unknown, and estimated that this SNR is one of the nearest and youngest SNR in our Galaxy: the estimated distance and age are 0.33 (0.26–0.50) kpc and 660 (420–1400) years, respectively.

The spectra of the Sloan Digital Sky Survey (SDSS) are being used to construct a catalogue of QSO absorption lines, for use in studies of abundances, relevant radiation fields, number counts as a function of redshift, and other matters, including the evolution of these parameters. The catalogue includes intervening, associated, and BAL absorbers, in order to allow a clearer definition of the relationships between these three classes. We describe the motivation for and the data products of the project to build the SDSS QSO absorption line catalogue.

Molecular cloud cores—whether stellar, non-stellar, proto-stellar, or pre-proto-stellar—have come to be recognized as key elements in the study of star formation. For both high-and low-mass stars, these cores hold key information for the final make-up of the stellar cluster and the physical processes by which the cluster and/or the individual stars form. In the case of massive stars, the chemical effects extend even beyond the molecular core, reaching into the photo-dissociated region produced by the harder spectrum of the massive stars. We discuss the directions in which these studies are taking us, with special attention given to those aspects which are unique to high-mass star-forming regions.

The Submillimeter Array located atop of Mauna Kea in Hawaii is a collaborative project of the Smithsonian Astrophysical Observatory and the Academia Sinica Institute of Astronomy and Astrophysics. The high angular resolution provided by the SMA is particularly suitable for studying massive star-forming cores which often exhibit strong (sub)millimeter continuum and spectral features but mostly locate within crowded regions at large distances. We report the latest SMA status and recent results in the area of massive star formation obtained with the array.

Currently two planetary systems around pulsars are known - discovered by the pulse timing technique, an indirect method. These planets were a surprise and gave rise to diverse planet formation scenarios, some of them very different to the common planet formation models around solar type stars and thus physically very interesting. Furthermore, neutron star planets are not only interesting themselves but also to study properties of the poorly understood neutron stars. After a summary about the current state of pulsar planets and the theoretical formation models, we present our own direct-imaging search for thermal emission of neutron star planets using the VLT. The project sample includes the fascinating radio-quiet isolated neutron stars, which are some of the closest and probably youngest neutron stars we know. Companions around them can only be found by direct imaging. Detecting planets around neutron stars by direct imaging differs significantly from using this technique for other, e.g. solar type, stars. As great advantage there is no need to reject the starlight of the primary.

We have studied the lithium abundance in 18 extremely metal-poor main-sequence turnoff stars as a function of [Fe/H] and $T_{\rm eff}$, using high-quality VLT/UVES spectra. The sample covers the range $-3.3\le [{\rm Fe}/{\rm H}]\le -2.5$, with half of the stars below [Fe/H] = −3.0. $T_{\rm eff}$ is determined from H$\alpha$ line profiles as well as from B-V, V-K, J-H and J-K colours. The behaviour of A(Li) as a function of metallicity is markedly different when different temperature scales are adopted. However, even when applying standard depletion corrections, it is a robust result that the Li abundance in extremely metal poor dwarfs is far below the prediction of standard big bang nucleosynthesis using a baryonic density consistent with the WMAP data.

Both optical CCD detectors and infrared detector arrays have steadily evolved over the past 5 years, and have reached very satisfactory levels of quantum efficiency and dark current. Optical CMOS detector arrays have rapidly improved and are beginning to compete with CCD detectors. A new development of great relevance for future instrumentation is the integration of the readout electronics into an integrated circuit in close proximity to the detector, or, in the future, its vertical integration with the detector array and multiplexer. This paper reviews the present status of these technologies and identifies opportunities and risks for the next decade.

The 8-instrument suite studied by the ESO community in the frame of the conceptual study of the 100 m OWL telescope is briefly presented. Potential capability for unique science and the main technical challenges are identified.

In order to use the lithium abundance of the Spite plateau to constrain the Big Bang Nucleosynthesis, one has to determine how much of the original lithium has been destroyed by the various physical processes that are known to operate in stellar radiation zones. These are briefly reviewed, with emphasis on the mixing occurring in tachoclines and on that generated indirectly by the transport of angular momentum through internal gravity waves.

In this contribution initial results are presented from a program to study in detail the stellar populations of dwarf Spheriodal (dSph) galaxies in three nearby groups. The long-term aim of the program is to assess the influence of environment in governing the evolution of these low-luminosity systems. Specific results described here include the detection and measurement of intermediate-age upper-AGB populations in dSphs in the M81 and Cen A groups, and the discovery that four of the five low-luminosity early-type dwarfs in the low density Sculptor group contain modest amounts of neutral hydrogen gas.

High-quality K-band spectra of point sources, deeply embedded in massive star-forming regions, have revealed a population of 20 young massive stars showing no photospheric absorption lines, but only emission lines. The K-band spectra exhibit one or more features commonly associated with massive Young Stellar Objects surrounded by circumstellar material: a very red color $(J-K) = 2$, CO bandhead emission, hydrogen emission lines (sometimes doubly peaked), and FeII and/or MgII emission lines. The CO emission comes from a relatively dense (${\sim}10^{10} \mathrm{cm}^{-3}$) and hot ($T\sim 2000$–5000 K) region, sufficiently shielded from the intense UV radiation field of the young massive star. Modeling of the CO-first overtone emission shows that the CO gas is located within 5 AU of the star. The hydrogen emission is produced in an ionized medium exposed to UV radiation. The best geometrical configuration is a dense and neutral circumstellar disk causing the CO bandhead emission, and an ionized upper layer where the hydrogen lines are produced. We argue that the circumstellar disk is likely a remnant of the accretion via a circumstellar disk.

Deep galaxy redshift surveys in the field around sight lines that probe OVI absorbers is a powerful method to investigate the nature of these absorbers and their correlation with galaxies. Here we present preliminary results of a study of fields observed with the Gemini/GMOS spectrograph centred on three low redshift QSOs known to probe a variety of OVI systems. Notably, some OVI absorbers appear to be associated with isolated, individual galaxies. Others are clearly found within large-scale structures but at substantial distances from any individual galaxy.

We report on an XMM-Newton observation of the supernova remnant (SNR) DEM L241 in the Large Magellanic Cloud. In the soft band image, the emission shows an elongated structure, like a killifish (Head and Tail), with a central point source, named as XMMU J053559.3–673509 (Eye). The Eye's spectrum is well reproduced with a power-law model. The source has neither significant coherent pulsations nor time variabilities. Its luminosity and spectrum remind us that the source might be a pulsar and/or pulsar wind nebula in DEM L241. The spectra of Head and Tail are well reproduced by a non-equilibrium ionization plasma model with over-abundant Ne and under-abundant Fe, suggesting that the progenitor of DEM L241 is a very massive star.

The distribution and composition of the dust and gas surrounding Young Stellar Objects (YSOs) is of continuing interest. Fortunately, rapid advances in observational capabilities have led to data of high spatial and spectral resolution, as well as the opportunity to observe in previously unavailable windows using satellites. Such high-quality data have motivated enhancements in theoretical models. Key to these models is the chemical evolution of the gas. Since the chemical evolution depends upon temperature, density, and time, the state and history of the source is encoded in the spatial distribution of the chemical abundances.

It is possible, using both parametric and detailed physical-chemical modeling, to constrain many source properties, and identify potential reactions of further laboratory interest. Using specific examples, I discuss some successes toward constraining the source properties, as well as challenges posed by current problems. Finally, I discuss the potential effect of infall dynamics and recent laboratory measurements of temperature programmed desorption of ices from grains on inferring source properties.

Dawn is the first mission to attempt to orbit two distant planetary bodies. The objects chosen, 4 Vesta followed by 1 Ceres, are the two most massive members of the asteroid belt that appear to have been formed on either side of the dew line in the early solar nebula. This paper describes the present status of the mission development and the plans for operation at Vesta and Ceres.

Neuhäuser et al. (2005a) presented evidence for a sub-stellar, common proper motion companion to GQ Lup, which is almost certainly a planet imaged directly, based on two independent mass estimates by means of theoretical models. The magnitude of GQ Lup b was determined by relative photometry compared to GQ Lup A. During a one-month monitoring of the primary star, we found is to be a variable with K= 6.9 to 7.3 mag (absolute photometry). Then, we re-observed GQ Lup A+b in May 2005, again with VLT/NACO. Due to the monitoring in April 2005, we could predict the exact K-band magnitude range of the primary during the new AO observation. Hence, we could determine a more precise error of the K-band magnitude of GQ Lup b by relative photometry compared to the primary. The new value is consistent with the previous estimate within the error margin, so that also the conclusions in Neuhäuser et al. (2005a,b) about its very low mass remain valid.

The activities in scientific research related to Commission 19 are mostly developed in the different institutions that have sent their reports here enclosed, in the different meetings that have been organized in related themes, and in the WGs of the Division 1. An important additional activity has been developed in the frame of precession and nutation. This research has been initiated by the Descartes Prize received by the Nutation Consortium in 2003.