The cosmic microwave background and the cosmic expansion can be interpreted as evidence that the Universe underwent an extremely hot and dense phase about 14 Gyr ago. The nucleosynthesis computations tell us that the Universe emerged from this state with a very simple chemical composition: H, 2H, 3He, 4He, and traces of 7Li. All other nuclei where synthesised at later times. Our stellar evolution models tell us that, if a low-mass star with this composition had been created (a “zero-metal” star) at that time, it would still be shining on the Main Sequence today. Over the last 40 years there have been many efforts to detect such primordial stars but none has so-far been found. The lowest metallicity stars known have a metal content, Z, which is of the order of 10−4Z⊙. These are also the lowest metallicity objects known in the Universe. This seems to support the theories of star formation which predict that only high mass stars could form with a primordial composition and require a minimum metallicity to allow the formation of low-mass stars. Yet, since absence of evidence is not evidence of absence, we cannot exclude the existence of such low-mass zero-metal stars, at present. If we have not found the first Galactic stars, as a by product of our searches we have found their direct descendants, stars of extremely low metallicity (Z ≤ 10−3Z⊙). The chemical composition of such stars contains indirect information on the nature of the stars responsible for the nucleosynthesis of the metals. Such a fossil record allows us a glimpse of the Galaxy at a look-back time equivalent to redshift z = 10, or larger. The last ten years have been full of exciting discoveries in this field, which I will try to review in this contribution.

Radial metallicity gradients are observed in the disks of the Milky Way and in several other spiral galaxies. In the case of the Milky Way, many objects can be used to determine the gradients, such as HII regions, B stars, Cepheids, open clusters and planetary nebulae. Several elements can be studied, such as oxygen, sulphur, neon, and argon in photoionized nebulae, and iron and other elements in cepheids, open clusters and stars. As a consequence, the number of observational characteristics inferred from the study of abundance gradients is very large, so that in the past few years they have become one of the main observational constraints of chemical evolution models. In this paper, we present some recent observational evidences of abundance gradients based on several classes of objects. We will focus on (i) the magnitude of the gradients, (ii) the space variations, and (iii) the evidences of a time variation of the abundance gradients. Some comments on recent theoretical models are also given, in an effort to highlight their predictions concerning abundance gradients and their variations.

The star formation and the subsequent metallic enrichment of spiral galaxies, occurring at the early phases of their evolution, produce emission lines whose contribution may change the colors of these objects. We have computed this contribution with consistent chemo-spectro-photometrical theoretical models in order to calculate the variations in the colors evolution.

The coalescence of black hole binaries is a significant source of gravitational wave radiation. The typically asymmetric nature of this emission, which carries linear momentum, can result in the recoil of the black hole remnant with velocities in the range 100 < Vrecoil < 3750 km s−1. The detectability of recoiling massive black holes (MBH) as off-nuclear QSOs is tightly connected with the properties of the host galaxy, which determine the MBH's orbit and fuel reservoir. We present the results of N-body simulations of recoiling MBHs in high-resolution, non-axisymmetric potentials. We find that if the recoil velocities are high enough to reach regions of the galaxy dominated by the generally triaxial dark matter distribution, the return time is significantly extended when compared to a spherical distribution. We also perform simulations of recoiling MBHs traveling in gas merger remnants, where large amounts of gas have been funneled to the central regions, In this case, the MBHs remain within R<1 kpc from the center of the host even for high recoil velocities (Vrecoil = 1200 km s−1) due to the compactness of the remnant galaxy's nuclear disk. We discuss the implications of both scenarios for detectability.

In 2007-2008 the authors found many magnetite microspheric particles in ground samples at the Trans-Carpathians mountains near the village of Tur'yi Remety. Their diameters are of 0.1 - 0.3 mm and they have Ni, Co and Cr as chemical composition. We think that these particles are part of the bright bolide of EN171101 which exploded above Trans-Carpathians mountains on Nov. 17, 2001.

Studying by the authors of paper of solar wind parameters, namely: density, speed and temperature and also a module of interplanetary magnetic field (IMF) intensity has allowed to find out in them fluctuations with the period of 399 days. From references it is known that this period coincidence with the synodic period of Jupiter. So long as close by the given period another source of such fluctuations is not known we have assumed that fluctuations with the period of 399 days are fluctuations with the synodic period of Jupiter. The change of the solar wind plasma parameters and IMF intensity can lead to the change of the Earth's magnetic field parameters and, as a consequence, to the change of charged particle fluxes in the Earth's magnetosphere. On this assumption the IMF intensity in the Earth's vicinity, geomagnetic disturbance (Kp-index) and riometer absorption for the years of 1986-1996 have been analyzed. The analysis of the data has shown the presence of certain changes of these physical parameters with the period of 399 days. When the Earth and Jupiter were found to be on the same magnetic field line, the IMF intensity was decreasing up to 3.0±0.57, the geomagnetic activity and riometer absorption were decreasing up to 5.2±1.46% and 9.4±2.63%, respectively.

The orientation of nineteen 0.8< z < 2.3 radio-loud quasars was measured using two independent methods. First, Hα was observed in the near IR using ISAAC at the VLT. The complex Hα emission lines were fitted with a range of models, some including emission from a flattened, extended accretion disk following Chen & Halpern (1989). The models were compared using the Bayesian evidence, and the disk axis angles recovered. Second, models were fitted to the ~10 MHz to 20 GHz radio spectral energy distributions (SEDs) to recover the jet angles, assuming that the emission is comprised of a broken power law arising from the radio lobes plus a Doppler-boosted core.

We describe a comprehensive multi-wavelength and multi-faceted program to understand a class of quasars we call post-starburst quasars, which may represent an evolutionary phase in mutual galaxy/black hole evolution.

Analysis of CCD observations of Phoebe, the 9th satellite of Saturn (visual magnitude of about 16.5), with a mirror astrograph ZA-320M at Pulkovo Observatory in Saint-Petersburg are presented. Photometric observations are performed both in the integral band of the telescope and in bands BVR of the Johnson system. Reference catalogues USNO-A2.0 (for R - filter and integral observations) and Ticho-2 (for V and B - filters) were used. Rotational light-curve data for Phoebe taken over a short time span (2 - 8 hours) for several nights are presented. Numerical investigation of the evolution of Phoebe's rotational dynamics is carried out. The probability of Phoebe's capture in resonant states that are distinct from 1:1 is estimated.

The recently completed AT20G survey provides the largest and most complete sample of high-frequency selected radio sources yet obtained, and offers new insights into the nature of the high-frequency active galaxy population. Here we focus on the optical properties of this survey which highlights the difference of the AT20G source population compared to other radio-selected AGN samples.

Fe ii comprises up to one third of the line emission in AGNs. For that reason it is an important coolant that needs to be taken into account to fully understand the energetics of the broad line region (BLR). As such, Fe+ is a potential diagnostic of gas density, column density, turbulence, temperature and continuum shape. However, understanding Fe ii is complicated because of the energy level configuration and different mechanisms that may contribute to the line emission.

Using a population number synthesis code, the theoretical time distributions of type Ia supernovae in starburst galaxies are calculated, using competing models for the formation of such events: the single degenerate (a white dwarf accreting matter from a late main sequence or red giant companion) and double degenerate (the merger of two white dwarfs) scenario. The code includes the latest results in determining the progenitors for both models. Examples are the mass stripping effect in the case of the single degenerate scenario and the differentiation between the α- (based on the balance of energy) and γ- (based on the balance of angular momentum) description of energy conversion during common envelope evolution of binaries. The shape and extent of the obtained delay time distributions critically depends on which formation scenario is used. Comparing these results to the latest observed distributions allows to draw conclusions about the constraints put on the theoretical models by these observations. We also specifically investigate the influence of the degree of conservatism during Roche lobe overflow on the delay time distribution. We conclude that the single degenerate scenario alone cannot reproduce the observed delay time distributions, and that most double degenerate type Ia supernovae are formed through a quasi-conservative Roche lobe overflow phase followed by spiral-in, as opposed to a double common envelope evolution.

We describe and analyze the color dispersion of LRG's at redshifts, z=0.4-0.5.

Quasars are the choicest objects to define a quasi-inertial reference frame. At the same time, they are active galactic nuclei powered by a massive black hole. As the astrometric precision of ground-based optical observations approaches the limit set by the forthcoming GAIA mission, astrometric stability can be investigated. Though the optical emission from the core region usually exceeds the other components by a factor of a hundred, the variability of those components must surely imply some measure of variability of the astrometric baricenter. Whether this is confirmed or not, it puts important constraints on the relationship of the quasar's central engine to the surrounding distribution of matter. To investigate the correlation between long-term optical variability and what is dubbed as the “random walk” of the astrometric center, a program is being pursued at the WFI/ESO 2.2m. The sample was selected from quasars known to undergo large-amplitude and long-term optical variations (Smith et al. 1993; Teerikorpi 2000). The observations are typically made every two months. The treatment is differential, comparing the quasar position and brightness against a sample of selected stars for which the average relative distances and magnitudes remain constant. The provisional results for four objects bring strong support to the hypothesis of a relationship between astrometric and photometric variability. A full account is provided by Andrei et al. (2009).

Globular cluster (GC) systems are powerful probes to study the evolutionary histories of galaxies, being tracers of major star fomation episodes (Brodie & Strader 2006). They are found around all major galaxies and are easy to see far beyond the local group. Age dating GCs therefore helps pinpoint epochs of major star forming events. Spectroscopic age dating though (Strader et al. 2005) is extremely time consuming and can only access the few brightest clusters. An alternative is to combine near-infrared (NIR) and optical photometry, and therefore have a better chance in lifting the age metallicity degeneracy than with optical colours alone. This approach relies in testing GC colours against simple stellar population (SSP) models. The first studies following this technique showed the possible existence of a high percentage of intermediate age (2-3 Gyrs) GCs in early-type galaxies known to contain old stellar populations from integrated light studies. Two strong cases can be listed: NGC 4365 (Puzia et al. 2002, Larsen et al. 2005) and NGC 5846 (Hempel et al. 2003). In the present study we combine NIR deep photometry obtained with the WHT/LIRIS instrument and archival HST/ACS optical images to determine g(F475W), z(F840LP) and K(2.2m) magnitudes and colours of GCs in 14 early-type galaxies.

The Kepler mission will obtain high precision, continuous lightcurves for more than ~150,000 stars over the next four years. Prior to primary mission operations, ten days of commissioning data were obtained for the ~52,000 brightest targets in the Kepler field. While Kepler's main goal is the discovery of transiting low mass planets, it will also provide a rich dataset for studies of variable stars. These commissioning data give a first glimpse of the amazing diversity of stellar variability Kepler will observe. Here, we discuss the tools we are currently developing to quantify variability in the Kepler data, and show initial results on the distribution of target stars in these metrics. Ultimately these measures will be used both to characterize the data and to select active rotationally modulated stars for rotation period determination.

We present the results of astrometric and photometric observations of comets and minor planets obtained at the Kiev comet station (Code MPC 585) of the Astronomical Observatory of Kyiv Shevchenko National University in 2006-2009. The 2318 position observations of 176 comets, 302 observations of 57 numbered minor planets, and 220 observations of 30 unnumbered minor planets were obtained. The accuracy of the astrometric observations of the comets is analyzed.

In a recent paper, da Silva et al. (2009), we report results of Li abundance analysis for nine young stellar associations, defined in Torres et al. (2008), from a high-resolution optical spectroscopic survey searching for associations containing young stars (SACY), among optical counterparts of ROSAT All-Sky X-ray sources in the Southern Hemisphere. They have applied a convergence method in the (UVW) velocity space and have determined nine nearby young associations in the sample. As they are young and with different ages, those associations form an interesting laboratory to test the Li depletion theory, as a function of the star age.

We present preliminary measurements of the central black hole mass MBH, and stellar mass-to-light ratio M*/LR, in the Brightest Cluster Galaxy of Abell 2162 (A2162–BCG), using integral-field unit (IFU) data from OSIRIS on Keck 2 with laser guide star adaptive optics (LGS-AO). Our results demonstrate early success in an ongoing effort to obtain stellar dynamical measurements of MBH in nine BCGs using ground-based AO.

We apply single- and multi-spacecraft techniques to search for currents sheets in the solar wind during the ICME event of 21 January 2005, using the Cluster magnetic field data. Two large-scale currents sheets are detected at the leading boundary of the ICME ejecta using the single-spacecraft technique, which exhibit physical characteristics typical of magnetic reconnection exhausts in the solar wind.