Infrared array detectors are a new and promising tool for investigating the properties of magnetic field concentrations in the solar photosphere. Array measurements provide large statistical samples of polarized line profiles and display the spatial organization of the magnetic field. The wavelength region near 1.6 μm has important advantages for magnetometry: spectral lines with magnetic sensitivites ranging from low to very high; low continuum opacity; high continuum flux; and the possibility of sub-arcsecond angular resolution with existing telescopes. Initial results have extended earlier work on the distribution of field strength and flux in plages and revealed new properties specifically connected with spatial structure. The quality and flexibility of near infrared magnetographs can be expected to improve rapidly.

Local Group galaxies allow us to test some properties of massive star evolution which are inaccessible in our Galaxy, in particular the effects of different metallicities. Thus, after showing that we still do not know the exact process by which massive stars are formed, we examine the differences in the distributions of O-stars, blue and red supergiants and WR stars in the Local Group. The number ratios WR/O and WN/WC are well accounted for by stellar models in which the mass-loss rates depend on the metallicity, Z, as predicted by stellar wind theories. The number ratio of red supergiants to WR stars is growing for decreasing Z. Although this behaviour is qualitatively well explained, the models need some extra mixing to fit the observational data. The same is true for the explanation of the He- and N-excesses in O, B and A supergiants. Rotation and related mixing processes certainly play a major role in massive star evolution. The relative number of Be-stars is higher at lower Z, which suggests that rotation is faster, also with more mixing, in small, irregular low-metallicity galaxies.

Advances in instrumentation and reduction methods are blurring the historical distinctions between various classes of double stars. One result of this is increasing confusion in double star nomenclature, as the conventions followed by different observers are sometimes incompatible. The Washington Multiplicity Catalog is presented as a means of developing a single nomenclature scheme for all types of doubles, as well as a comprehensive database for all duplicity information.

In this talk I give a short overview of models for spectral lines in Be stars disks which I think are quite instructive. I then examine the arguments for my own model assumptions and discuss selected topics concerning radiative line transfer calculations in three dimensions. We show that symmetric Hα emission lines of Be stars can be understood in terms of Keplerian disks. It is also demonstrated that one-armed global disk oscillations provide the best available solution to understand the long-term V/R variations in Be star emission lines.

We have been searching the northern sky for ultra-narrowband carriers of intelligent extraterrestrial origin at 21cm wavelength. The dual-polarization 65,536-channel receiver has a resolution bandwidth of 0.03Hz, matched to the Drake-Helou spreading of the interstellar medium. This maximizes signal/noise ratio, and simultaneously rejects carriers of terrestrial origin. The results of 15 months of observation are summarized.

The yellow D lines from neutral sodium are some of the most useful interstellar absorption features for tracing out low density optically thin interstellar material. Hobbs (1978) compared column densities of Nal as determined from the D lines with HI column densities derived from ultraviolet observations and found values of N(NaI)/N(H)<6.3x10-9 in 18 sight-lines with very low reddening, with the exact value of the ratio apparently a function of temperature. If this ratio limit holds for diffuse clouds in nearby space, we expect that observations of the Nal D2 lines at the 3 mA level can be used to trace out nearby clouds with column densities in the range of ≥2.5x1018 cm-2. Thus sensitive measurements of the Nal D lines are a useful way of observing nearby neutral cloud material. With this in mind, we have chosen high-resolution observations of the yellow sodium lines as a means of locating and mapping nearby low density interstellar clouds.

The theoretical study of the evolution of massive stars has considerable relevance to many branches of observational astronomy. As an example, one may mention, first, the direct application of theoretical models in interpreting the observed properties of supergiants, and second, the use of calculations of the nucleosynthesis taking place in these stars, together with observed supergiant mass loss rates and supernova calculations, to estimate the rate and type of nucleosynthetic enrichment of the interstellar medium by supergiants.

We investigate the properties of the dark halo of the dust-lane elliptical galaxy NGC 3108. This galaxy contains a large massive gaseous disk, which shows rapid and regular rotation. That makes NGC 3108 a target for measurements usually feasible only for spriral galaxies. Combining spectroscopic measurements of the disk in the optical- and the radio regime, we provide a reliable rotation curve of the galaxy out to 3 Reff and show that the rotation curve does not decline up to a radius of 5.5 Reff corresponding to 28 kpc.

The observations of the sun by the large Pulkovo radio telescope [1] began in 1956 December. In accordance with the antenna dimensions, a fan-beam diagram about one minute of arc in width and one degree in height was expected (at λ = 3.2 cm).

Several properties of the 131 galaxies known within 9. 1 Mpc are investigated. 88 of these galaxies are concentrated into eight groups, leaving 33 percent of true field galaxies. There are E/S0 and S0 galaxies among the field galaxies; their types must be of cosmogonic origin. the groups have small velocity dispersion which limits the mean mass-to-light ratio for the different types of group galaxies to m/L < 20. Within the supergalactic plane the deviation from an ideal Hubble flow are small: the changes of ΔHO/<HO> with distance and direction are not larger than ten percent; the radial component of the peculiar motion of field galaxies is <25 km s−1. the differential luminosity function of S/Im galaxies is well approximated by a Gaussian with and . the luminosity function of E/S0 galaxies is much flatter with a possible minimum, separating true E's and dwarf ellipticals (Reaves, 1977). the sample galaxies are strongly concentrated toward the supergalactic plane; at a distance of 4 Mpc of the plane the luminosity density drops to half its value. There is also a pronounced luminosity density decrease with increasing distance from the Virgo cluster centre; at a distance of 30 Mpc the density has decreased by more than a factor of 104. the best estimate of the mean luminosity density within a sphere of 30 Mpc radius centered on the Virgo cluster is 1.5 · 108 L⊙ Mpc−3.

The first quantitative evidence for a large scale density excess or “metagalactic cloud” including the Local Group was obtained by Holmberg (1937) and confirmed by Reiz (1941). the present concept of the Local Supercluster (LSC) as a flattened aggregate of field galaxies, small groups and larger clouds centered at the Virgo cluster was formulated 25 years ago (de Vaucouleurs 1953) even before large-scale superclustering was recognized as a general phenomenon. See review papers in Vistas in Astronomy (1956), Soviet Astronomy (1960), Science (1970), Publ. Astron. Soc. Pacific (1971), and IAU Symp. No. 63 (Abell 1974).

The massive OB stars in our Galaxy form predominantly in the warm giant molecular clouds which constitute the spiral arms. The clouds are subject to a variety of mechanisms which retard or prevent further contraction, but are nevertheless able to form stable “cores”. In the regime of subsonic internal motions, the cores may be regarded as potential protostars. The formation of massive cores, which then form massive stars, may initially be determined by the statistics of fragmentation, but may then be a feedback process, once underway, due to the steep increase of the minimum Jeans' mass with increasing temperature of the surroundings. This concept is the basis for the model of bi-modal star formation, and its implications for the initial mass function and the distribution of massive stars and metallicity gradients in the Galaxy.

MERLIN positions of 12 radio stars are used to link the provisional Hipparcos reference frame to the International Celestial Reference Frame. The accuracy of the link using these radio stars is 2.3 milliarcseconds. Further observations are planned to check the accuracy of the link in the future.

Woltjer: Dr. Field raised the issue of the discrepancy between some estimates of the amount of graphite. I wonder if any of the authors have a comment on this point?

The complex radio source Sgr A is embedded in a region near our Galactic Center. The dynamical center of our Galaxy is considered to be Sgr A*, the compact non-thermal radio source. Dynamical mass within ~0.1 pc from Sgr A* has been estimated to be ~ 3×106 M⊙. This places Sgr A* to be a candidate of a massive blackhole (Eckart and Genzel, 1997 and reference therein).

ESO has two telescope projects: the NTT (New Technology Telescope) with 3.5 m aperture and the VLT (Very Large Telescope) with 16 m equivalent aperture. The former is already in the engineering phase and should be completed in 1987; the latter is still in the study phase and will be described at this conference by our colleague, D. Enard.

This paper is concerned with the primary support system of the NTT. The basic principles and layout of this support have already been described in the literature 1,2,3).

Many nearby galaxies show optical evidence for low-luminosity AGNs that are far less luminous than classical Seyfert nuclei and QSOs. LINERs, the most common variety of such emission-line objects, comprise ~ 1/3 of nearby galaxies, and may serve as an important “missing link“ between normal and Seyfert galaxies. To shed light on the physical origin of LINERs, which remains controversial, we are conducting a high-resolution continuum survey of a representative sample of galaxies using the VLA to search for compact radio cores. We additionally discuss the dramatic radio variability in the LINER nucleus of M81.

The existence of meteoroid streams is indicated by the regular appearance of coherent meteor activity at specified times during the year. Since it is the interaction of the meteoroid with the atmosphere that is detected, the meteoroid has to be greater than about 100 micrometers in radius. Observation of these interactions gives information on individual meteoroids as well as collective phenomena. It is generally agreed that streams form through the ejection of dust particles from the surfaces of comets and asteroids at speeds considerably lower than the orbital speed. The subsequent motion of these particles is affected by gravitational perturbations from the planets and the effects of solar radiation forces. This review is intended to present an overview of the development of the subject and of our current state of knowledge.

Exoplanet search programs need to study how to disentangle radial-velocity (RV) variations due to Doppler motion and the noise induced by stellar activity. We monitored the active K2V HD 189733 with the high-resolution SOPHIE spectrograph (OHP, France). We refined the orbital parameters of HD 189733b and put limitations on the eccentricity and on a long-term velocity gradient. We subtracted the orbital motion of the planet and compared the variability of activity spectroscopic indices (HeI, Hα, Ca II H&K lines) to the evolution of the RV residuals and the shape of spectral lines. All are in agreement with an active stellar surface in rotation. We used such correlations to correct for the RV jitter due to stellar activity. This results in achieving a high precision on the orbital parameters, with a semi-amplitude: K=200.56±0.88m⋅s−1 and a derived planet mass of MP=1.13±0.03 MJup.

Palomar and Tautenburg Schmidt plates with a base line of about 35 years have been measured with the Automated Photographic Measuring (APM) system in Cambridge (UK) in order to obtain the proper motions of the Galactic dwarf spheroidal satellites (dSph) in Draco and Ursa Minor with respect to a well defined extragalactic reference frame. The investigations were encouraged by the accuracy level achieved for the mean absolute proper motions of galactic globular clusters (0.05 arcsec/century from 25 years base line Tautenburg plate pairs) which is comparable to the expected proper motion of the Draco and Ursa Minor dSph assuming tangential motions of about 100 km/s. Different methods for the removal of systematic errors in the absolute proper motion introduced by the measuring and reduction process are discussed. The more accurate relative proper motions of individual stars in both dSphs obtained by Stetson (1980) and by Cudworth, Olszewski & Schommer (1986) provide an external comparison and are also used to obtain the mean absolute proper motion of the dSphs.