We describe a newly refined procedure for making optical identifications of radio sources in Abell cluster fields observed with the Molonglo Observatory Synthesis Telescope (MOST). The method is based on past experience but uses a range of new tools to improve the reliability and production rate of identification lists. The COSMOS/UKST Southern Sky Object Catalogue was used to make preliminary identifications which were then inspected visually with the assistance of computer generated overlays of the MOST images and the Digitized Sky Survey (DSS). The overlaid images were essential for securing identifications for the extended sources prevalent among nearby clusters.

We find 21±1·5% of the radio sources are identified with galaxies and 4·6±0·7% with QSO candidates in a sample of 927 radio sources in 27 cluster fields. We make a preliminary attempt to separate cluster radio galaxies from interlopers on the basis of absolute magnitudes. A strong concentration of radio galaxies was found at projected distances less than 100 kpc from the cluster centres and a weaker concentration for projected distances of 100–500 kpc.

Current results from the experiment by Reines et al (1980) on the oscillation of neutrinos from one flavour to another, if confirmed, require a non-zero rest-mass for the neutrino. Corroborative evidence can be adduced from the astrophysical consequences. In particular, the long-standing ‘missing light’ paradox in rich clusters of galaxies is solved (c.f. Cowsik and McClelland 1973), and more recent difficulties in reconciling the chronology of the Universe with both the primordial abundance of He4 and the cosmological mass density are eased (c.f. Symbalisty et al 1980). Finally Lewis (1981) shows that the concept also solves the problem of obtaining dynamically relaxed clusters of galaxies with feasable formation times. As a result, elliptical galaxies are necessarily formed from the material of a proto-cluster amid a high density of low-velocity neutrinos. This paper makes a preliminary estimate of the maximum neutrino content of elliptical galaxies.

It is known that in the radio spertrum the limb of the quiet sun is brighter in the equatorial regions than near the pole. But most of the available theoretical calculations of the brightness distribution over the quiet sun have been made with the assumption of spherical symmetry. We have therefore calculated two-dimensional distributions at several decimetre and metre wavelengths, taking account of the observed asymmetry in the north-south direction. Newkirk’s method of ray-tracing was used, the calculations being made with a CDC 3600 computer. Some of the preliminary results (particularly for a sunspot minimum period) are presented here; they indicate that the electron temperature of the solar corona has a value of about 1 to 1.5 x 106 °K.

Although the maser hypothesis for anomalous OH emission encounters difficulties it has not been seriously questioned because, as pointed out by Turner, no alternative has been available. The following ideas might suggest that there is an alternative hypothesis for anomalous OH emission.

We present a list of bright (< 17 mag) southern QSOs and bright (< 11 mag) stars that may be suitable for the Hubble Space Telescope link between the Hipparcos astrometric reference frame and the VLBI extragalactic frame. The QSOs have been selected from various lists of radio objects and identifications. The stars have been selected from the Strasbourg (CDS) data base and from the Preliminary Second Cape Photographic Catalogue, and supplemented with stars measured from the SERC IIIa-J Schmidt survey. The list of QSOs and stars have been included in the Hipparcos and HST schedule of observations.

The photometric observations (UBVRI) of nine cool R Coronae Borealis (RCB) stars have been collected at Mt John University Observatory, New Zealand, over a period of twelve years. The analysis of the magnitude–colour and colour–colour diagrams for the recovery phase demonstrates that all declines exhibit a similar asymptotic approach to their normal brightness. Declines return to maximum brightness along a line with essentially the same slope that does not depend on the star or the depth of the decline. Assuming a uniform obscuration of the photosphere by the dust cloud during the recovery phase, the extinction properties of the material were determined. The ratio of total to selective extinction (RV) for the RCB stars in our sample is in the range 2.5 to 4.6, indicating that the obscuring dust has extinction properties similar to that of the interstellar dust. Observations have been compared with the theoretical extinction curves for different sorts of grains.

A laboratory astrophysics facility for the study of the terrestrial analogues of interstellar dust grains is being developed in the Physics Department, University College, Australian Defence Force Academy. The facility consists of a gas handling system for the preparation of samples, a closed-cycle cooler and specimen chamber, and a Fourier Transform Infrared (FTIR) Spectrometer capable of high resolution (0.3 cm−1) and high sensitivity measurements, currently from 1-25 μm. The layout and construction of the laboratory are described, and the proposed initial experimental program aimed at determining the optical constants of ices over a wide wavelength range for comparison with astronomical observations is discussed.

Spectroscopic observations of BF Cygni performed at the Haute-Provence Observatory in 1981 August, October and November are presented. The spectrum of BF Cyg was dominated by strong emission lines of H I, He I, [O III] and [Ne III]. Emission lines of He II and N III were weak. The spectrum of the star displayed dramatic variations during our observations. The intensities of Balmer lines, Balmer continuum and He I lines clearly increased from August to October, while the lines of [Ne III] and [O III] showed inverse variability.

Observations at a number of frequencies indicate that for at least two pulsars the average pulse shape has a slow but quite definite frequency dependence. Figure 1 shows average pulse shapes for CP 1919, CP 0950 and CP 1133. With the exception of those at 408 MHz these results were obtained at Parkes. The 408 MHz pulse shapes were obtained at Jodrell Bank by Lyne and Rickett. Circumstances of the observations are listed in Table I. Linearly polarized feeds were used at all frequencies.

Truncated modal expansions have provided a powerful, reasonably accurate and flexible approach to the problem of non-linear thermal convection. They permit tractable numerical solutions of three-dimensional cellular motions, as well as readily accommodating large density variations, time dependence, rotation and magnetic fields.

The workshop programme of a new first year university astronomy subject with low capital costs incorporates diverse learning experiences: planisphere, time around the world, sundial, telescope, computer simulation, planetarium, spectroscope, poster, debate, night-time observatory trip. The practical activities, used to address specific learning objectives, emerged clearly as a major strength of the subject as evaluated by the mixed student cohort.

Various authors have reported observations of the flux and circular polarization for the three stars PG 1658 + 441, PG 1533 − 057 and K 813 − 14. On the basis of the observational data, the stars were classified as magnetic white dwarfs. To place constraints on the magnetic field strengths and geometries of these stars, the relevant authors qualitatively compared the data with available theory and, in two cases, used a model of optically thin hydrogen threaded by a magnetic field.

In this paper we use a more detailed model for magnetic white dwarfs to assess the results previously obtained for these three stars. We find that, in two cases, the observed spectra can be explained by the Zeeman splitting of hydrogen lines in a stellar magnetic field which takes the form of a dipole situated at the centre of the star. The circular polarization data for PG 1658 + 441, however, may indicate a field geometry for this star which is significally different from that of a centred dipole.

We present 2.2 μm maps of four southern HII regions. Although each of these objects has been extensively studied at radio wavelengths with low spatial resolution, they have so far (with the exception of G333.6 – 0.2) received little attention in the infrared. As a first step towards understanding the structure of these objects we have therefore produced images of each in the K-band (2.2 μm) continuum.

The adjective ‘high’ when applied to the resolving power of radiotelescopes, has a meaning that has changed very rapidly during the last twenty-five years. In the late 1940s a resolving power of one degree was considered to be ‘high’.

Optical spectra of the ejecta of SN 1987A taken at the AAT now cover seven years of evolution. In recent years, SN 1987A has been in a phase known as freeze-out. The timescales for recombination have exceeded those of energy deposition, and the ionisation structure has become fixed. During this phase, cooling is slow and the optical spectrum has been extremely stable. Our latest spectrum, however, shows significant change. [FeI] and [FeII] emission from iron-rich clumps has dominated the optical emission from the supernova over the last four years. All the [FeII] features have disappeared in our latest spectrum from December 1993 and model fits of [FeI] features indicate that these clumps have cooled to the critical temperature of 1000 K. They may be entering a phase of rapid cooling known as the infrared catastrophe. In addition, emission at high velocities has strengthened, in line with the predictions of freeze-out. SN 1987A may be entering a new, and previously unobserved, phase in supernova evolution.

As has been previously stated (van der Borght) the lengths l1, l2, l3 and l4 are functions of and so a discussion of these lengths is in fact a discussion of the f’s. For a first approach to a determination of these f’s, a standard Vitense2 model of the convection zone—with mixing length l, is used. We assume that l = H. The variables we need are kz, which are the vertical wave number associated with the characteristic eddy, the average vertical velocity, and the average (non-dimensional) temperature fluctuation. These quantities are approximated, using the following relations

It is well known that a magnetic field has an inhibiting effect on thermal convection. It is also likely that a magnetic field might have a marked effect on the preferred cell-size and it is therefore of some importance to investigate the effect of such a field on finite amplitude convection. We restrict ourselves to fluids in which the Boussinesq approximation holds. For astrophysical application, especially in a study of the convective layer of the Sun, one should consider the compressible case but unfortunately the full compressible equations are much more difficult to handle numerically. In any case, the integration of the equations for the incompressible case will yield at least an indication of the effect of a magnetic field.

Some special issues to which IUE observations have provided crucial insight are presented. The arguments leading to the definitive identification of Sk−69°202 as the progenitor of the LMC supernova are reviewed, and a preliminary determination of the reddening toward SN 1987A, based on the IUE spectra of stars 2 and 3, is discussed. Recent observations at the predicted position of the SN ultraviolet light echo are reported, and evidence, albeit circumstantial, is provided that a UV echo has been detected. Some consequences of this result are explored. The relevance of this observation lies in the fact that a UV echo, if really detected, would give direct information of the spectrum of the SN at the time of the shock breakout.

The internal constitutions of the terrestrial planets Mars, Venus and Mercury are investigated through the use of ‘equations of state’ empirically derived for particular internal zones of the Earth. The equations usually take the form of tabular relations between the pressure p and density p, temperature dependence being treated as of secondary consequence. In using p rather the full stress tensor in solid zones, i.e. in using a hydrostatic theory, the effects of strength and deviatoric stress are also treated as of secondary consequence. Except for the use of data on the ellipticity ∊ of figure of a planet to provide evidence on the moment of inertia I, the planets are treated as spherically symmetrical.