The present Astronomy Advisory Committee (AAC) was set up by the then Minister for Science and the Environment, Senator J. J. Webster, in July 1979 following a Government review of astronomical facilities carried out by an interdepartmental committee (IDC) in 1978-1979. The IDC was assisted by an expert sub-committee, whose report Review of Observatories (1978) has since been published. The AAC consists of a chairman and ten members drawn from the astronomical community in Australia. It is serviced by the Department of Science and the Environment.

The most extensive studies of supernova remnants (SNRs) in the past have taken place at radio and optical wavelengths.

J. Rahe of Bamberg reported on IUE observations of comets Sargent (1978) and Bradfield (1980).

The 1.04 m telescope and auxiliary instrumentation conceived some ten years ago, are now operational and starting to produce results. Whilst the original purpose of the telescope was high dispersion spectroscopy alone at Coudé focus, access to a folded Cassegrain focus has been added to enable photometric observations to be made.

Speckle interferometry (Labeyrie 1970, 1976) is one way of overcoming the blurring effect of the atmosphere in optical astronomy. When a short exposure is taken of an image, the seeing disc (typically several seconds of arc across) is seen to contain structure (speckles) down to the resolution limit of the telescope (0″.03 arc for the Anglo-Australian telescope). A second exposure 10 or so milliseconds later will show a different pattern of structure because the atmospheric irregularities will have changed. Multiple stars or source components within the same angular range of atmospheric irregularity (i.e. isoplanatic patch several seconds of arc across) will produce similar but displaced speckle patterns, and geometrical details of the components can be obtained from an autocorrelation analysis of the speckle pattern (Dainty 1975).

Given an ordered set of samples {ai} of some function, then the autocorrelation of that function is the mean lagged product of these samples.

A proposal for the siting of additional 14 metre antennas for the Fleurs Synthesis Telescope (FST) was previously presented by Christiansen (1976). Since that time, difficulties have arisen which preclude the use of two of the locations. In addition, solutions to the problems of data reduction for irregular antenna spacings have been found (Frater and Skellern, 1978; Frater, 1978; Frater, 1979). It has now been possible to choose the locations of the final antennas to optimise the performance of the array within broader geographic constraints — subject now to the availability of sites on ‘friendly’ land.

The Llanherne telescope is a meridian transit instrument with an instantaneous bandwidth of two octaves in the range 35 to 150 MHz, and was constructed primarily for studying the low frequency properties of pulsars. The antenna is a 78 × 156 metre filled aperture phased array comprising 4096 wire dipole elements arranged in a 64 × 64 matrix. Uniform illumination of the elements produces a single pencil beam response which is scanned electronically along the meridian from Declination -90° to +30°. The beamwidth at 100 MHz is 1 degree in right ascension and two degrees sec(Dec.) in declination and varies proportionally with wavelength, giving a transit time of 4 sec(Dec) × 100/f(MHz) minutes between half power points.

The Tidbinbilla NASA Deep Space Network tracking station near Canberra employs 64-m and 34-m antennas for deep space vehicle communication. Regular use is made of the facilities for radio astronomy via a host country agreement between the United States and Australia. To support the expanding astronomical use of the station, and in particular for the Tidbinbilla two-element interferometer (Batty et al. 1977), a small computer was installed early in 1980 to control observations. The system will also be used for as much data analysis as possible to minimize off-site computing.

A small astronomical observatory has been constructed on the edge of the Macquarie University campus at North Ryde in Sydney. It will be used primarily for photoelectric observations of variable stars. Further improvements to the present observing system are being planned and observations have already started on β Cepheids.

The conventional method of measuring the radiation diagram of an antenna is to rotate it in the field produced by a fixed point source located in its Fraunhofer zone (Hollis et al. (1970)). With the very large antennas typically used in radio astronomy this presents difficulties. For example, to measure the 64 m telescope at ANRAO, Parkes at frequencies in the OH transition lines band (1.6-1.7 GHz), the source, to be located in the Fraunhofer zone, must be located at least 50 km away and then at a sufficiently high angle to allow measurements free from ground effects to be made. Clearly there are no terrestrial means to accomplish this.

Baseline ripple measurements are of two general kinds, those associated with on-source mechanisms and those with off-source mechanisms (Poulton 1974; Morris 1974). We are here principally concerned with on-source baseline ripples, which occur when a strong continuum radio source is present in the beam. The ripples are particularly conspicuous (Padman 1977, 1978) with a large instrument, such as the Parkes 64-m telescope, where the ripple period is rapid. Here baseline uncertainty becomes especially severe for the detection and study of wide lines, such as the H/He complex and the formamide multiplet near 1.54 GHz. Off-source baseline ripples also occur because of other effects, but in principle they can be removed by subtracting a reference-region spectrum taken while tracking the telescope over the same hour-angle range at the same declination under stable conditions. Improvement of the off-source baseline ripple which arises from stray radiation would also be expected to result from the technique described here.

Polytropic models have played a significant part in the historical development of stellar structure theory and in other related branches of theoretical astronomy such as stellar pulsations and rotation. In modern astronomy polytropic solutions, because of their wide range of density distributions and our ability to introduce them analytically if necessary, now have an acknowledged role in large scale numerical experiments especially during the developmental stages.

The two important parameters which essentially determine the nature of the convective regime, and consequently the total heat transported by convective processes, across an unstable layer in a star are the Rayleigh and Prandtl numbers defined by (Chandrasekhar 1961)

where ν is the coefficient of kinematic viscosity, x is the coefficient of thermal diffusivity and α, g, d, ΔT are respectively the coefficient of thermal expansion, acceleration due to gravity, depth of the fluid layer and temperature difference across the layer. In addition, the horizontal scale of the convection cell is determined by the horizontal wave number a and for convection to be established R must be greater than the critical value at marginal stability, Rc, which is a function of a, given by

when the free boundary conditions apply.

The traditional classification of solutions of the Lane-Emden equation

into E, F and M types is based on the value of the invariant quantity

In a previous paper (Van der Borght 1979) the techniques developed for studying finite amplitude convection in a compressible medium were applied to an investigation of super-granulation in the Sun. Assuming that the instability is due to He+ recombination, a model was derived which seems to indicate that convection in the upper 8000 km of the Sun may occur as an overtone and not as a fundamental mode. This investigation yielded results which were very close to those obtained from standard mixing-length theory.

All studies of circulation in stars have been based on a linear perturbation analysis (e.g. Sung 1975). This analysis establishes criteria for the onset of circulation and, if the perturbations remain weak, allows the circulation pattern to be determined. (For a survey see Tassoul 1978).

When two stars are in orbit about each other, tidal forces cause an exchange of energy and angular momentum between the orbital motion and the fluid motion of each star about its own centre of mass. The orbit is progressively altered, and one or both stars may be catastrophically disrupted.

The statistical theory of strong three-body interactions (Monaghan 1976a, b, Nash and Monaghan 1978) is based on the assumption that the motion of the system in phase space is ergodic, and that the energy and angular momentum are the only isolating integrals. The a priori phase space is infinite because the system is not confined by walls, but this is only a formal difficulty since the numerical calculations show that the motion takes place in a finite region of ordinary space and this fact can be incorporated in the statistical description. The probability density of the system in phase space is essentially Gibb’s Micro-Canonical ensemble.

Misner Thorne and Wheeler (1973), (page 629) suggested that a freshly formed White Dwarf star of several solar masses would, if slowly — rotating, collapse to form a neutron star pancake which would become unstable and eventually produce several, possibly colliding, neutron stars.