In this review we present a brief discussion on the observational evidence in favor of the presence of temperature variations, and conclude that many planetary nebulae show spatial temperature variations that are larger than those predicted by 1D static chemically homogeneous photoionization models. To determine accurate chemical abundances it is necessary to know the cause of these temperature variations and several possibilities are discussed. The importance of this problem is paramount to test the models of stellar evolution of low and intermediate mass stars and of the chemical evolution of galaxies. We conclude that the proper abundances for chemically homogeneous PNe are those derived from recombination lines, while for the two-abundance nebular model the proper heavy element abundances relative to hydrogen are those derived from visual and UV collisionally excited lines adopting the $t^2$ values derived from $T_e$([O III]) and $T_e$(Balmer).

Starburst galaxies are characterized by uncommonly high star formation efficiencies, but it remains unclear what physical conditions in the molecular gas produce this high efficiency. Invariably, high star formation efficiency is associated with high column densities of molecular material (e.g. the Kennicutt-Schmidt law), but what are the conditions in the molecular clouds in starburst galaxies? Direct observations of starburst are difficult or impossible with current instruments, so I present the properties of GMCs in the Local Group as a starting case and then extend the analysis of GMC properties to nearby systems with surface densities of gas intermediate between the Local Group and starbursts. Rather than being constant, molecular cloud properties follow a continuum with significant variation across the Local Group and the intermediate surface density systems. Concomitant with these variations in the macroscopic properties are significant changes in the internal pressure and densities of molecular clouds, which implies significant variability in the initial conditions of the star formation process.

We have derived a new Hβ absorption index definition, which is fully optimized as an age indicator for old and intermediate-aged stellar populations. Rather than using stellar spectra, we employed theoretical SEDs at moderately high resolution for simple stellar populations of different ages and metallicities. The new index, which is virtually insensitive to metallicity, provides us with improved abilities for lifting the age-metallicity degeneracy, that affects the standard Hβ Lick/IDS index definition. Among other advantages this new index does not require spectra of extremely high signal-to-noise and it can be easily applied to observations of faint galaxies or surveys data.

The observing program of the Nordic Near-Earth-Object Network (NEON) accrues knowledge about the physical and dynamical properties of near-Earth objects (NEOs) using state-of-the-art inverse methods. Photometric and astrometric observations are being carried out at the Nordic Optical Telescope. Here, the NEON observations from June 2004–September 2006 are reviewed. Statistical orbital inversion is illustrated by the so-called Volume-of-Variation method. Statistical inversion for spins and shapes is carried using a simple triaxial shape model yielding analytical disk-integrated brightnesses for both Lommel-Seeliger and Lambert scattering laws. The novel approach allows spin-shape error analyses with the help of large numbers of sample solutions. Currently, such spin-shape solutions have been derived for 2002 FF12, 2003 MS2, 2003 RX7, and 2004 HW. For (1862) Apollo, an unambiguous spin-shape solution has been obtained using the conventional, convex inversion method and, for (1685) Toro and (1981) Midas, the conventional method has been applied repeatedly to map the regime of possible solutions.

One of the most interesting constraints on star formation models comes from the study of multiplicity of young stars as a function of mass. While multiplicity studies of low-mass T Tauri stars have been quite exhaustive, an unbiased and systematic investigation of multiplicity among intermediate-mass Herbig Ae/Be (HAEBE) stars is still lacking. We are therefore conducting a photometric and spectroscopic survey of HAEBE stars to detect companions, establish their physical association with the primary and investigate their properties. The frequency and degree of multiplicity of HAEBE systems will provide new constraints on their formation mechanisms. In this paper we present preliminary results of the high resolution imaging part of the survey, carried out with the adaptive optics system Altair-NIRI on Gemini North. Of 72 stars observed, we find 44 possible binaries or multiples, including at least 25 not previously known.

High-dispersion spectroscopic observations of the neutral Homunculus and the ionized Little Homunculus, ejecta of η Car, are being analyzed to determine the relative abundances of metals. Thousands of lines of neutral and singly-ionized metals and molecules seen in the Homunculus suggest that this oxygen-, carbon-poor, nitrogen-, helium-rich gas contains very different dust grains likely devoid of metal oxides. The gas to dust ratio is likely much larger than the canonical 100:1 implying that the 12 M⊙ estimate of the ejecta is a lower limit.

Numerical simulations of convection-driven dynamos in rotating spherical shells are employed to better understand the observed strength and geometry of planetary magnetic fields. The model computations cannot be performed for realistic values of several of the control parameters. By varying parameters within the accessible range, it is possible to derive scaling laws for the magnetic field strength and the flow velocity in the dynamo region and for the dipole moment. Our scaling laws suggest that, even though diffusivities are far too large in the models, diffusive processes do not play an important role, just as in planetary cores. Extrapolating the scaling laws to planetary values of the control parameters leads to reasonable predictions for the field strength in the dynamo region and fits the observed dipole moments decently, in particular in the cases of Earth and Jupiter. For Mercury, which does not fit well when applying the scaling laws in a straightforward way, a model is proposed in which the upper part of the fluid core is stably stratified and the dynamo operates only in its deep regions. The time-varying dynamo field must diffuse through the stable region and is attenuated by the skin effect. The model explains why Mercury has a very weak but probably dipole-dominated magnetic field.

We show how the expansion of classical Galactic Hii regions can trigger massive-star formation via the collect & collapse process. We give examples of this process at work. We suggest that it also works in a turbulent medium.

Choosing either an empirical or a theoretical stellar library in stellar population models is a subject of debate. Theoretical models do not perfectly match high-resolution spectra of real stars, but we can use them to overcome the natural limitations of empirical libraries on covering abundance patterns that differ from solar neighbourhood stars. Here, we will mix stellar population synthesis models based on both theoretical and empirical libraries, in order to explore a new method to constrain the enhanced α-elements pattern on galaxies.

We summarize the main observational features that seem to recur more frequently in the ULX population. We speculate that low metal abundance, and clustered star formation triggered by molecular cloud collisions are two fundamental physical requirements for ULX formation. In this scenario, most ULXs are formed from recent stellar processes, have black hole (BH) masses <100 M⊙, and do not require merger processes in super-star-clusters.

GEMINI-S+CIRPASS configuration has been used to obtain 490 high quality spectra, centred in 1.3 microns of the NW-SE oriented, central 80 × 200 pc of NGC 5236 (M83), with spectral resolution of 3200. We determine the kinematics of this region with 0.36 arcsec sampling, sub-arcsec resolution. Disk-like motions are detected in Paβ at parsec scales around: a) the optical nucleus (ON), b) the dynamical centre of the CO velocity map (Sakamoto et al 2004) coincident with the K–band center (hereafter KC; Thatte et al. 2000), located 50 pc to the W of the optical nucleus, and c) the hidden condensation (hereafter HN; Mast et al. 2006), now more precisely located at 120 pc to the N-NW of the optical nucleus. The disk around ON has a radius of 10–15 pc and those around KC and HN can be traced approximately up to 40-50 pc from their kinematical centres. Rotation curve fittings using Satoh like spheroids give masses of 2–4×106M⊙, 10–15×106M⊙ and 15–20×106M⊙ respectively. N-body simulations using Gadget2 (Springel, 2005) show that ON, KC and HN will merge in 20-50 Myrs. A question that arise immediately is if this degree of dynamical activity is peculiar of M83 or it is a common behaviour, seen in this galaxy in all its dramaticity due to its small distance from us.

After a brief survey of the foundations, development and the present status of astronomy education at all levels, a review of research in astronomy in Serbia and in Montenegro is given.

Stellar multiplicity is a fundamental astrophysical property. In addition to being the only physical basis for accurate mass determination, this parameter is believed to influence important aspects such as planet formation and stability. Contrary to earlier expectations, recent studies have shown that even against selection biases, as many as 23% of the planetary systems reside in multiple star systems (Raghavan et al. 2006)). Leveraging recent efforts in identifying stellar and substellar companions to solar-type stars, and augmenting them with targeted observations, we are conducting a comprehensive survey, aimed at providing a modern update to the seminal work of Duquennoy & Mayor (1991). The details of our sample, survey methods, and some preliminary results are presented here.

We present the latest observational results on the halo PN, H 4–1 (PN G049.3+88.1). The H$_{2}$ 1–0 S(1) 2.122 $\mu$m emission image of H 4–1 showed the existence of an equatorial disk with two outer arcs in this object. In order to reveal the internal kinematics making this complex structure, we performed spatial and spectral high-resolution spectroscopy with the HDS (High Dispersion Spectrograph) of the Subaru 8.2m telescope. The HDS observational results showed the presence of a high-velocity ($\ge$ 40 km s$^{-1}$) collimated outflow.

From Yohkoh and SoHO observations, the magnetic reconnection is considered as a main energy release mechanism of the solar active phenomena. In this study, we try to reproduce GOES X-ray light curves (1–8 $\AA$) of solar flares using a model incorporating the radiative and conductive cooling and the magnetic reconnection heating.

The state and discovery rate of current NEO surveys reflect incremental improvements in a number of areas, such as detector size and sensitivity, computing capacity, detection software efficiency and availability of larger telescope apertures. The result has been an increase in the NEO discovery rate. There are currently eight telescopes ranging in size from 0.5-1.5 meters carrying out full-or part-time systematic surveying in both hemispheres. The sky is covered 1-2 times per lunation to V1~9, with a band near the ecliptic to V2~0.5. We review the current survey programs and their contributions towards the Spaceguard goal of discovering at least 90% of the NEOs larger than 1 km.

Evolutionary synthesis models (ESM) have been extensively used to obtain the star formation history in galaxies by means of SED fitting. Implicit in this use of ESM is that (a) for given evolutionary parameters, the shape of the SED is fixed whatever the size of the observed cluster (b) all regions of the observed SED have the same weight in the fit. However, Nature does not follow these two assumptions, as is implied by the existence of Surface Brightness Fluctuations in galaxies and as can be shown by simple logical arguments.

In Bosnia and Herzegovina astronomy teaching is almost nonexistent. There are only several courses within universities and they are usually given by physicists who themselves have had only elementary courses in astrophysics. When educational outreach is in question, the situation is even more grim. On the other hand, there is a huge interest for astrophysics in the student population. There are several solutions and possibilities which I will present, together with a discussion of the main obstacles which need to be overcome.

Several recent luminous events that have been identified initially as supernovae (SNe) are probably not genuine SNe at all. Instead we argue that these events are more likely the outbursts, or super-outbursts, of very massive stars in the luminous blue variable (LBV) phase. At least two of these events are analogous to the Great 1843 Eruption of η Carinae.

We calculate evolution, collapse, explosion, and nucleosynthesis of Population III very massive stars with 500 M⊙ and 1000 M⊙. It was found that both 500 M⊙ and 1000 M⊙ models enter the region of pair-instability but continue to undergo core collapse to black holes. For moderately aspherical explosions, the patterns of nucleosynthesis match the observational data of intergalactic and intercluster medium and hot gases in M82, better than models involving hypernovae and pair instability supernovae.

Our results suggest that explosions of Population III core-collapse very massive stars contribute significantly to the chemical evolution of gases in clusters of galaxies. The final black hole masses are about 500 M⊙ for our most massive 1000 M⊙ models. This result may support the view that Population III very massive stars are responsible for the origin of intermediate mass black holes which were recently reported to be discovered.