Observations of NGC 5128 (Cen A) show that this giant elliptical galaxy contains few globular clusters. The fact that the number of globular clusters per unit luminosity in E galaxies has a range of ∼ 102 indicates that different ellipticals were formed in differing physical environments. It is pointed out that more data on the frequency with which globular clusters occur in elliptical galaxies might place interesting constraints on theories of galaxy clustering.

Intercomparison of the Local Group galaxies IC 1613 and the SMC shows that differences in the frequency of cluster formation also occur among Irregular galaxies.

It is pointed out that globular clusters associated with distant galaxies probably start to outnumber galactic stars for B > 31.

The discovery that the LMC supernova remnant N63A is situated in the small association N2030 shows that this object must have been formed from a star with a main sequence mass > 30 M⊙.

Finally we show that E3, which is one of the faintest known galactic globular cluster, was decimated by tidal forces. Due to the interplay of equipartition and tidal effects this cluster has been severely depleted in single stars while retaining many (presumably binary) blue stragglers.

Distances to clusters are not more accurately determined today than twenty years ago. Effects of different abundances in different clusters can seriously influence distance determinations. There is, however, no immediate call for a revision of the cluster distance scale as obtained by curve fitting assuming the distance of the Hyades to be known.

Three types of associations are presently recognized. These are OB, R, and T, and represent, respectively, concentrations of O and B type stars, reflection nebulae, and T Tauri stars, in certain regions of the sky. OB and T associations are identified on objective prism plates; R associations may be found using direct plates such as those of the Palomar Sky Survey. All associations are intimately connected with what appear optically as dark clouds and are now detected as sources of molecular line emission and known as molecular clouds. Often, all three types of associations are found within the same cloud complex (eg, Mon OB1). However, there are also examples of T associations (Taurus) and R associations (Mon R2) which are not connected with recognized OB associations.

The aim of this paper is to give a review of our knowledge of the chemical composition of young groups of stars in the Galaxy, i.e. open clusters and associations with ages less than about 109 years. In particular I shall discuss if abundance differences between these groups of stars do occur, and how large these possible differences can be. Such information is important in many astronomical fields. Thus, abundance differences between star clusters complicate the determination of their distances by ZAMS-fitting, and make the distance scale in the Universe more uncertain. Comparisons between theoretical isochrones and cluster sequences in color-magnitude diagrams with the purpose of testing the theory of stellar structure and evolution are also much more difficult if differences in abundances have to be taken into account. On the other hand the determination of abundances of clusters and associations as a function of their ages and places of formation give important information on the chemical evolution of our galaxy, in particular because abundances, ages and space velocities for clusters and associations can be determined much more accurate than for single stars.

This paper reviews recent astrometric progress in determining the Hyades cluster distance, emphasizing critical assessment of the precision and accuracy of the observations. Substantial improvement in the trigonometric parallaxes yields a mean Hyades distance modulus m - M = 3.25 ± 0.08 mag, nearly twice as precise as previous parallax results. New proper motions from three independent sources yield a mean distance modulus 3.31 ± 0.06 mag. The close agreement of the recent astrometric results suggests that the overall mean Hyades distance modulus 3.30 mag may be used with confidence in cosmic distance scale calibrations.

A new compilation of distance data for the Galactic globular clusters is used to estimate the distance to the Galactic center, RO. Three different ways of using the space distribution of the clusters lead to RO = (8.5 ± 1.0) kpc. The problem of the space distribution of the clusters in the Galactic nuclear region is briefly discussed.

An analysis of observational astrometric, photometric, spectroscopic data for the Hyades cluster is performed in order to compare Hyades G dwarfs to the sun. Internal structure computations are also used to compare the solar ZAMS with the Hyades ZAMS and to discuss the constraints existing between distance and chemical composition for the cluster.

The Sco OB2 Association is convenient for investigation as it has a high galactic latitude and is therefore remote from the confusion of the galactic plane. Its distance is accurately known and this permits fairly precise estimates to be made of the Lyman continuum photon fluxes responsible for the radio emission. It includes the ρ Ophiuci dark cloud where star formation is occurring.

In this paper we investigate the effect of mass loss by stellar wind on the evolution from the main sequence to the He exhaustion stage of stars in the range of mass 20 to 100 M⊙ with low metal abundance. To this purpose we compute the set of evolutionary sequences with initial mass 20, 30, 40, 60, 80, and 100 M⊙ and chemical composition parameters X=0.700, Z=0.001. The models are first computed at constant mass to provide the fundamental network to which we compare the mass losing models. This choice of the initial chemical composition is aimed to represent the case of luminous supergiants in the Small Magellanic Cloud. The rate of mass loss follows the formulation of Castor, Abbot and Klein (1975), but it incorporates the effect of different metal content in the regions of high effective temperatures in the HR diagram. The rate of mass loss for models at low effective temperature is given by the acoustic flux mechanism according to the formulation of Chiosi, Nasi and Sreenivasan (1978). The results are compared with those of Chiosi, Nasi and Sreenivasan (1978), and those of Chiosi, Nasi and Bertelli (1979) for normal metal abundance supergiant stars of the Galaxy. On the basis of the present results we suggest an interpretative scenario for the existence of single WR stars in galaxies of different chemical composition. These results allow us to interpret also the different percentages of WR's among subclasses that are observed in the Galaxy, LMC, and SMC (Conti and Vanbeveren, 1979).

In this paper we propose a model for the chemical evolution of the solar neighbourhood and the galactic disk as well. The model takes into account the inflow of primordial gas, and the time scale associated with the process of disk formation. We follow the same physical description and formalism adopted by Chiosi (1979). However, by releasing the approximation of instantaneous recycling, we are able to describe the chemical history of the galactic disk in much better detail than in Chiosi (1979). A set of eight elements (H,D,He3,He4,c+0,N,n-rich, heavy) is used to describe the chemical composition of the galactic gas and inflowing material. The disk is supposed to be represented by several independent shells, whose surface mass density is thought to depend on radial distance from the galactic center and age of the galaxy. The rates of mass accretion and star formation follow the formulation of Chiosi (1979). To better approximate the results from dynamical models of disk galaxies, we have taken into account the known fact the time scale of disk formation varies with the distance from the galactic center, being of the order of 1×109 y in the innermost, and up to 10×109 y in the outermost, regions of the disk. From the body of solutions we have explored, we can derive the following results, which are shortly summarized for the case of our best model of chemical evolution of the disk only.

For some years now, we have been slowly accumulating uvby, β data on numerous open clusters, with the various telescopes and photometers at KPNO. Analysis of the data, when combined with available UBV and MK data, has been done for most individual cluster stars. Such data and analyses have been published for most clusters and are in preparation for a few others.

Recent investigations of stellar chemical composition made it possible to estimate some parameters of the galactic disc chemical evolution: the abundance gradient, d[Fe/H]/dR, and rate of enrichment, d[Fe/H]/dt. Practically all the conclusions of these investigations were based on data on chemical composition of single stars, for which the error in age determination is considerable.

UBV observations of stars in the small and compact cluster Tr 15 located 20 arcmin north of Eta Carinae confirms its physical connection to the OB aggregate comprising TR 14, Tr 16 and Cr 228. Its corrected distance modulus is Vo–Mv = 12.1, with a mean interstellar absorption of Av = 1.4 ± 0.2 mag. Two very red variable stars, RT Car, close to the cluster (2 arcmin), and BO Car, about 8 arcmin southeast, appear to be related to the cluster itself. These two are the only bright red supergiants in the whole region, and from the RICK measures the probable membership of both is verified. The extinction law from the B-V, V-I diagram indicates a higher value of R in comparison with the normal one, but lower than the amount derived earlier for the Tr 14/16 (Feinstein, Marraco, and Muzzio 1973), and which is also confirmed with new measures in this photometric system. The extinction law for the young cluster NGC 6611 (Feinstein, in preparation) appears to be the same, in spite of being probably younger.

Some simple comparisons have been made between models of main sequence (MS) stars and the Hyades main sequence with the aim of investigating the effects of small changes in the stellar opacities, the zero point of the temperature scale and the assumed distance modulus for Hyades cluster have on the inferred metallicity of the Hyades. Three grids of MS models were constructed using the Cox and Stewart (1970a,b) opacities. Furthermore, taking a rather conservative view with regard to future changes in opacity compilations, another grid was constructed with opacities 20% higher than the Cox-Stewart opacities. Following the procedure outlined by Gough and Weiss (1976), the mixing length required for constructing a solar model was found to be 1.36. Because recent photometric and spectroscopic work (Barry et al. 1978; Hardorp 1978) suggests that the sun may be redder than traditionally believed, i.e., (B-V)⊙ = 0.66–0.67 instead of 0.63 mag, two temperature scales have been used to transform the MS models to the CM diagram.

At visual inspection of objective-prism plates of Milky Way regions one frequently detects pairs or sometimes higher multiples of spectra which are so similar in appearance and so close together that they form a conspicuous configuration for the eye. A statistical analysis shows that the observed occurrence of this phenomenon, down to a certain limiting magnitude and up to a certain value of the angular separation of the components, considerably exceeds the expected one - if it should be considered as produced entirely by random coincidence. Therefore it is reasonable to assume a physical explanation behind this sort of agglomeration. According to the working hypothesis it is essentially a part of very loose or star-poor clusterings which do not show a sufficiently high degree of contrast against the surrounding galactic stellar background to be discovered “directly”. The phenomenon might thus be comparable to an optical multiple system, although it is produced by members of a physical cluster of some kind. In connection with a large survey of the Southern Milky Way, carried out at the Stockholm and Uppsala observatories, several thousands of such coincidences have been registered. About a hundred of them have been subjected to a special investigation, intended to give an answer to the question about their physical interpretation. Although the methods have been neither very rational, nor always point-to-point reliable, the scrutiny has shown pretty well that an overwhelming majority of the “candidate” objects do reveal stellar clusterings of various types. In fact, it has been possible to distinguish between at least four more or less well-defined types of objects in the shape of stellar clusterings. 1. Relatively ordinary clusters, a few of which are already known or even well-known. The “rediscovery” is then some sort of a confirmation of the working hypothesis. 2. Very loose clusterings. 3. Extremely small and star-poor clusters, possibly cluster remnants. 4. Multiple systems with extreme separation between the components, maybe the ultimate stage of a cluster in disintegration. The relative frequency of the four interpretations in order will approximately be: 1–20%, 2–35%, 3–20%, 4–10%. In addition, there is also a certain admixture of spurious objects without astrophysical interest.

The catalogue contains data for 1130 galactic clusters. Each cluster has 255 available storage places. Most of these are reserved for positional, descriptional and physical parameters. In the present version the following items are included:

1. – Cluster name, OC1 No. (Alter et al. 1970)

2. – R.A., Dec (1950.0), R.A., Dec. (2000.0), precession for 10 years, galactic longitude, galactic latitude

3. – Data on peculiar stars (Feinstein 1979): Type, number, references

4. – Part of Dixon's (1976) catalogue: POSS chart type, chart No., coordinates for chart centre (R.A., Dec), position on chart, largest published angular diameter, magnitude of brightest star, Trumpler class, nebulosity

5. – Part of Bochum-Strasbourg catalogue (Kluke et al. 1975): Selected angular diameter, distance, magnitude of brightest star, spectral class, total magnitude, colour excess

6. – Buscombefs (1978) compilation: Radial velocity, distance, colour excess, total apparent magnitude, total absolute magnitude, linear diameter, age, mass

7. – Basel data (Becker and Fenkart 1971; Fenkart and Binggeli 1979): Photometric system, colour excess, interstellar extinction, distance, spectral type of hottest star, colour type of bluest star, linear diameter, type of observation

8. – van den Bergh-Hagen (1975) data: Angular diameter, richness

9. – Lyngå (1979) compilation: Selected angular diameter, references (various other parameters with references will be included later).