Mare than 100 symbiotic stars are now known. A catalogue of them, complete to 1984 January 1, is presented. Finding charts are given for all examples, and optical spectra for the majority. A table summarises the observational material at X-ray, ultraviolet, infrared and radio wavelengths.

There are two major difficulties associated with theoretical studies of star formation. The first of these is that the dominant physical process or processes leading to star formation have not been identified. The second is that realistic calculations at an appropriate level of accuracy have been impossible to carry out. The result has been that only minor advances have been made on the early work of Jeans (1929) and Hoyle (1953). Much greater progress can be expected in the next few years both because observations of infra-red sources have given us much more information about the site of star formation, and because access to the current generation of very fast computers is becoming more common.

Some years ago the full non-linear equations, within the one mode approximation, describing finite amplitude convection in a compressive medium with polytropic structure were derived (Van der Borght 1977). It is the purpose of the present paper to report on the numerical integrations of these equations and to show how these can be used to construct a convective model of granulation. In this way one may gain some insight into the structure of the outer layers of the Sun.

The NASA Voyager spacecraft missions to the outer planets have provided a wealth of observational data with regard to the physical and chemical properties of the attendant satellite systems. Although the gaseous nebula discs from which these satellites are suspected to have formed are no longer present, these data provide at least some basis from which the characteristics of individual nebula can be deduced.

Although scientific astronomy has a long and illustrious history in Australia, it was not until 1895 that the first astronomical society was formed. This was the New South Wales Branch of the British Astronomical Association (see B.A.A. 1894-5; Gale 1895a,b), and before the end of the century it was joined by others in Melbourne and Brisbane (B.A.A. 1897-8; Editor’s Note 1979; Ellery 1901:13; Thomson 1897). These societies and their predecessors, the Astronomy Branches of the Royal Societies of New South Wales and South Australia (Waters 1980), were the mainstay of astronomical activity – both professional and amateur – in nineteenth century Australia, providing as they did regular meetings, library facilities, and avenues for publication and celestial observation.

An intriguing problem in cosmogony concerns the ability of a planetoid embedded in a nebula disc to clear a gap around its orbit. The application of density wave theory to this problem has demonstrated that a significant exchange of angular momentum can take place between a planetoid and a disc (Goldreich and Tremaine 1980). The torque exerted by the disc on the planetoid can result in orbital drifting of the latter, which may play an important role in the aggregation process (Hourigan and Ward 1983). In fact, in the absence of significant deformation of the nebula, the radial orbital drift rate of a planetoid increases with planetoid mass. In this case, it would be expected that only one or two planetoids would sweep out the nebula, a situation not compatible with present observations. The orbital drift resulting from the generation of density waves therefore requires a limiting mechanism.

One of the most difficult tasks facing theoretical astrophysics today is to find a satisfactory model for the convective transport of energy in regions where the temperature gradient is superadiabatic. A number of such models have been proposed, such as the mixing-length theory and its extensions (Vitense 1953, Böhm-Vitense 1958, Spiegel 1963, Travis and Matsushima 1973 a, b, Parson 1969), to take into account the combined effects of convection and turbulence but it is generally agreed that, to-date, no satisfactory theory has been put forward.

Theoretical investigations of non-linear convective motions quite often assume that either the Boussinesq or the anelastic approximations can be used.

A large number of barred spiral galaxies contain a ring-like structure surrounding the bar. This is known as an inner ring if the bar terminates at the ring. Structures which are not closed but which appear to be related phenomena are given the name pseudo-inner rings by de Vaucouleurs (1959).

The relevance of the results for the total heat energy transported across a fluid layer by convective motions, obtained from the time integrations of the set of non-linear partial differential equations for hydromagnetic convection, has already been designated in a previous contribution (Lopez and Murphy 1982). Some differences in the form of the boundary conditions adopted for the magnetic field disturbance, H, have been noted in other publications where the interaction of convection and a magnetic field has also been considered. The solutions of the time-dependent equations, referenced above, illustrate that the magnetic boundary conditions have a determining role in the resultant convective state for some ranges of values in parameter space.

Mestel, Wang and Westfold (1984; ‘MWW’) have recently introduced a pulsar magnetosphere model in which electrons leave the star with non-negligible, but not highly-relativistic, speeds, and flow with moderate acceleration along magnetic field lines before reaching a limiting surface, near which rapid acceleration occurs. Such moderately accelerated flows are analysed here. A second class of flows, which do not encounter a region of rapid acceleration, is found.

Of the attempts to model the Magellanic system as the result of tidal interactions, only the works of Lin and Lynden-Bell (LLB 1982) and Murai and Fujimoto (MF 1981) can be considered to be successful.

The temporal behaviour of Rayleigh-Benard convection has attracted considerable attention in recent years, both from an experimental and theoretical point of view. Experiments (eg. Gollub and Benson 1980) have demonstrated a complicated array of non-linear behaviour, as well as the need for a model which will at least qualitatively describe what is observed.

Barred spirals are well-known to include several ‘distinct components’ or morphological structures in the light distribution (Sandage 1961; de Vaucouleurs 1959; Kormendy 1979). In addition to the bar, spheroid, and disk components, one often observes ring-like enhancements at discrete relative positions within the disk. These inner rings (r), outer rings (R), and nuclear rings (nr) have been the subject of recent, fairly intensive observational (Buta 1984a; Kormendy J979; de Vaucouleurs and Buta 1980a,b; Athanassoula et al. 1982) and theoretical (Schwarz 1979,1981,1984a,b,c; Simkin, Su, and Schwarz 1980) research, and it now seems well-established that most rings are linked to dynamical resonances with the bar.

For a spherically symmetrical distribution of gaseous matter in gravitational equilibrium the total pressure, density and other physical variables are all functions of the radial distance measured from the centre.

Cyclotron lines have been observed in the X-ray spectra of two pulsed sources: Her X-1 (Trümper et al. 1978) and 4U 0115 + 63 (Wheaton et al. 1979). The generally accepted model for these objects involves an accretion flow from a companion star in a close binary system onto small regions close to the magnetic poles of a strongly magnetized neutron star. Immediately above the surface, matter is confined in an accretion column by the magnetic field.

If computer speed and storage keeps increasing at the present rate a three dimensional numerical code modelling the exact equations governing general relativistic collapse will soon be possible; however, at present it is necessary to use simplifying approximations. Provided the general relativistic effects are limited to a ‘small’ perturbation, the post-Newtonian equations of Chandrasekhar (1965) should be adequate. These equations take the form of the Newtonian equations for a self gravitating fluid with extra terms to incorporate the 1/c2 contributions, where c is the speed of light. The numerical solution of these equations can be achieved using any method appropriate for three dimensional Newtonian hydrodynamics.

In recent years, a large amount of work has been directed towards understanding the process of star formation. However, despite these efforts, there still remain areas largely unexplored, where theories are only justified by approximate qualitative arguments rather than fully three dimensional calculations.

In theories of the heating of the solar corona a number of authors have recently considered the propagation and damping of fast and slow magnetohydrodynamic waves, in the form of surface waves localized on the interfaces of coronal flux tubes (Ionson 1978, Wentzel 1979, Roberts 1981, Cramer and Donnelly 1983). The damping of these waves occurs, in addition to a rather weak global damping due to viscous or resistive dissipation, by means of a localized absorption at a so-called ‘resonance’ in the density or magnetic field profile forming the flux tube. At such a resonance, the wave frequency is equal to the local value of the Alfven wave frequency, in the case of Alfven resonance absorption, or at the local slow mhd wave frequency, in the case of the ‘cusp’ or ‘compressive singularity’ resonance in a finite pressure plasma.