AE Aqr is a cataclysmic variable consisting of a magnetised white dwarf with a spin period of 33 s, and a K-dwarf companion. Because of the rapid spin the magnetosphere of the white dwarf the matter that is flowing over from the secondary cannot accrete onto the white dwarf, and rather it is ejected from the system. AE Aqr is subject to extended flaring activity at all wavelengths from radio via optical to X-rays. I present observations of AE Aqr at 345 and 850 GHz using the LABOCA and SABOCA bolometers on APEX. These observations are good enough to distinguish individual flares at both 345 and 850 GHz, and the SABOCA observation is the first measurement of the system at 850 GHz.

Optical and radio measurements of polarization can be combined to find the configuration of the magnetic field throughout the Crab Nebula. The component in the line of sight is found from the radio rotation measure.

New measurements of polarisation at 11 cm with a resolution of 7′ x 14′ are combined with previous results to show that the rotation measure is fairly uniform and near −25 rad m−2 near the centre, but that it becomes irregular near the edges. It rises to 300 rad m−2 in the filaments, possibly indicating a concentration of electrons about 10–100 cm−3.

The ways in which amateurs may increase their chances of discovering comets were described. Amateurs discover a considerable proportion of comets, but their contribution is greater among long-period comets. The relative proportions of short-period comets is revealing: 1 in 2 for professional astronomers, 1 in 8 for amateurs. Professional discoveries are largely a by-product of searches for asteroids: the comets have low inclinations (i < 30°) and are faint (m1 > 14). Amateurs are most successful in areas close (<60°) to the Sun. Typical apertures are 150-mm, and most comets are brighter than magnitude 10.

Past results show that there is a strong correlation between number of observers and number of discoveries. Several amateurs have discovered comets at great elongations with larger telescopes (≥ 400 mm). The comets tend to be fainter (10 < m1 < 12). Several comets have been discovered with simple equipment (200- or 300-mm telephoto lenses) down to magnitude 13.

Calculations of the distribution of discoverable comets show that an average of 14 comets (9 < m1 < 14) are missed per year.

The Astrophysics Data System (ADS) is an integral part of the Astronomy Digital Library and the collaboration Urania. It provides access to 1 million references and connects these references with many other information centers and their data, such as on-line journals, object databases, and scanned journal articles. This article describes some of the features and links between the ADS and other on-line services.

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.

The problem of calculating the mass distribution of meteorites and their influx rate can be resolved into three sections; (a) the flux of meteorites hitting the surface of the Earth must be calculated (b) the mass distribution of these meteorites must be assessed, care being taken to include the effect of fragmentation in the atmosphere and (c) atmospheric ablation, which is a function of mass, velocity, composition and zenith angle must be taken into account. The final result will give the meteoritic influx to the Earth's upper atmosphere and its mass distribution.

Probable dust counterparts of arching structures are looked for in two cases, (a) the Eridanus expanding shell, Heiles (1976) and (b) the extended Sco-Cen feature, Weaver (1977). Apparently the color excess data may be used to derive distance and dimension estimates of these structures.

21-cm line observations with the Westerbork Synthesis Radio Telescope of a dust and molecular filament at the boundary of the Draco Nebula (l≈ 91°, b≈ 38°) reveal a jet-like neutral hydrogen feature funneling through an outlet in the low velocity shock front at the interface between the Draco Nebula and the surrounding gas. The jet-like feature is apparently connected with a high velocity filament at VLSR = -180 km s-1. We suggest that the soft x-ray emission observed in the area is thermal bremsstrahlung produced by the deceleration of high velocity gas in galactic gas.

Wolf-Rayet (short: WR) stars are characterized by the bright and broad emission lines which dominate their spectra. This class was originally established for Pop. I stars, distinguishing a nitrogen (WN) and carbon (WC) sequence according to the dominating lines. Wolf-Rayet (specifically, WC) type spectra are also shown by a considerable fraction of central stars of planetary nebulae.

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).

Low and intermediate mass stars leave the Asymptotic Giant Branch (AGB) when the mass in their H-rich envelope is less than about 0.01 M⊙, and the high mass loss drops several orders of magnitude. The central star rapidly evolves to the left part of the HR diagram along a track of constant luminosity (e.g. Schönberner 1983). In principle the evolution of the central star to higher Teff and the expansion and cooling of the AGB remnant are easy to calculate. In practice several complicating factors arise which make it much more difficult to predict the morphology and properties of post-AGB stars, such as binarity, post-AGB mass loss and aspherical AGB mass loss. Binarity of post-AGB stars affects the morphology of the circumstellar environment, and it affects evolutionary timescales and surface chemical abundances of the components in the system. This review discusses some properties of binary post-AGB stars.

The integral field spectrograph TIGER, in operation at CFHT since a few years, has been successfully used on a large variety of astrophysical objects, ranging from the planet Mars to distant radio-galaxies and quasars. This review discussed the peculiarities of the TIGER design and gives the main characteristics of the instrument. Two examples of scientific applications are presented to highlight the new possibilities offered by integral field spectrography. Finally the OASIS project dedicated to the CFHT adaptive optics bonnette is briefly presented.

The metallicity-sensitive (U – G) colors from the new homogeneous catalog of photographic RGU data in seven high-latitude fields have been used to determine the larger-scale metallicity distributions of the Galactic population components. For the thick disk, preliminary analysis based on our best structural models provides a mean metallicity 〈[M/H]〉 = −0.6 ± 0.3dex and a marginal vertical metallicity gradient ≈ −0.1dex/kpc. The observed color distributions are further consistent with the (old) thin disk having mean abundance 〈[M/H]〉 = −0.3 ± 0.2dex and abundance gradient ∂[M/H]/∂z = −0.6dex/kpc.

We present a model to map the 3D distribution of dust in the Milky Way. Although dust is just a tiny fraction of what comprises the Galaxy, it plays an important role in various processes. In recent years various maps of dust extinction have been produced, but we still lack a good knowledge of the dust distribution. Our presented approach leverages line-of-sight extinctions towards stars in the Galaxy at measured distances. Since extinction is proportional to the integral of the dust density towards a given star, it is possible to reconstruct the 3D distribution of dust by combining many lines-of-sight in a model accounting for the spatial correlation of the dust. Such a technique can be used to infer the most probable 3D distribution of dust in the Galaxy even in regions which have not been observed. This contribution provides one of the first maps which does not show the “fingers of God” effect. Furthermore, we show that expected high precision measurements of distances and extinctions offer the possibility of mapping the spiral arms in the Galaxy.

Accretion from many small planetesimals to planets is reviewed. Solid protoplanets accrete through runaway and oligarchic growth until they become isolated. The isolation mass of protoplanets in terrestrial planet region is about 0.1-0.2 Earth mass, which suggests giant impacts among the protoplanets in the final stage of terrestrial planet formation. On the other hand, the isolation mass in Jupiter's and Saturn's orbits is about a few to 5 Earth masses, which may be massive enough to trigger gas accretion onto the cores. The isolation mass in Uranus and Neptune's orbits is as large as their present cores. Extending the above arguments to extrasolar planetary systems that are formed from disks with various initial masses, we also discuss diversity of extrasolar planetary systems.

Photography of the second epoch of the Lick Proper Motion Program (Wright 1950) was started in 1968. The original plan (Vasilevskis 1954) was modified in several respects. It was decided to carry out a pilot program first, before the start of a full coverage of the sky accessible from Lick. It was also decided to make use of the new lens corrected for yellow light (Vasilevskis 1964), in addition to the blue lens used for the first epoch. The aims of the pilot program were formulated: (1) carry out the necessary error investigations, (2) develop methods and procedures to a stage of routine, (3) derive proper motions of stars measured, and (4) attempt to arrive at some astronomical conclusions based on these motions. The program was limited to 97 fields nearly uniformly distributed over the sky north of -23° all these fields were photographed, measured and reduced, 78 of them contain a sufficient number of galaxies for proper motion reference. This report will be limited to presenting a few results obtained from the first crude analysis of proper motions that became available only a week ago. These results, therefore may change significantly in the process of further analysis.

The present-day birth rate of planetary nebulae, 5·10−12 PN/pc3yr according to Cahn and Wyatt (1976), seems somewhat high compared to white dwarfs, for which a redetermination, including the statistics of Sion and Liebert (1977), yields 2·10−12 WD/pc3yr to within a factor of two. However, an increase of the distance scale for PN by a factor of 1.3 compared to Seaton (1968) - necessary in order to shift the extremum of PN radial velocities to the distance of the galactic center (9 kpc), and to increase the luminosities of the central stars from the position given by Pottasch et al. (1977) to a minimum value compatible with evolutionary constraints (Weidemann, 1977a) - brings birth rates of PN and WD into almost complete agreements.

PC 11 (HD 149427, PK 331-5 1) is classified as a young planetary nebula with strong OIII 4363Å and a Zanstra temperature of TZ = 27000K. It is also classified as (D′ — type) yellow symbiotic star with A — F type companion. It is an IRAS source with detached cold dust with far intrared (IRAS) colours similar to planetary nebulae. The IUE short wavelength (SWP) spectra show emission lines due to OIII] (1661/1666Å). NIII] (1746/1754Å) CIII] (1907/1909Å). The OIII] and NIII] emission lines show significant variation. Variation in the strength of CIII] is not very significant. The strength of OIII] has decreased and NIII] has increased. The long wavelength (LWP) spectrum shows stellar continuum (A-F) and absorption lines due Mg II 2800Å feature. It also show emission lines at 2772Å (?) 3133Å −3140Å (very strong) (OIII, [FeV], 3209Å (He II?) ([FEII]). The variation in the strength of emission line due OIII] and NIII] and the presence of stellar continuum (A-F) suggests that the central star of PC 11 is a binary.

A summary is given of the presentations delivered at IAU Symposium 231.