Following the detection of a high flux density from Saturn at 21.2 cm by Davies and Williams and the confirmation by Kellermann, it has been known that the radio emission from Saturn is enhanced at long wavelengths. The Molonglo cross telescope has searched for this emission at 73.5 cm on two occasions, the first in 1967 November when the planet was stationary, and the second during the opposition of 1968 October. Between these dates, installation of preamplifiers on the EW arm doubled the sensitivity of the cross so that although the same procedures were used on both occasions, this paper is based almost entirely on the recent results.

This paper is the second report since 1984 on the photometric monitoring of long-period eclipsing binary stars at Yonsei University Observatory using a 61-cm reflector.

The first daily maps showing the two-dimensional radio brightness distribution over the Sun were produced at Fleurs ten years ago when the 64-antenna grating cross was completed. The maps had a resolution of 3′ arc at λ = 21 cm.

When the Fleurs field station was given to the University by CSIRO in 1963 it was decided to use the antennas of the grating cross and add to them four or more larger antennas (45 ft diameter) to produce a pair of high resolving-power compound interferometers.

When a star of mass ≳ 2M⊙ collapses there does not appear to exist any physical mechanism to prevent total gravitational collapse, unless in some miraculous way the star always manages to blow off enough mass for it to settle down into a stable neutron star or white dwarf configuration. General relativity is needed in order to handle the ultimate situation, and the theory predicts a critical radius ρ = 2m (in units such that G = c = 1) at which the coordinates in the Schwarzschild solution

become invalid.

Those solutions which have so far been obtained to the problem of a star with both rotation and a magnetic field have been for certain special cases, mostly time-independent. It is known that, except for stars with special rotation laws, a rotating star in hydrostatic equilibrium cannot maintain thermal equilibrium without generating slow meridional circulation of matter. It is also known that an axially symmetric field with no azimuthal component tends very strongly to keep the star in a state of isorotation, with the angular velocity constant along field lines. A magnetic field also tends to upset thermal equilibrium and produce meridional circulation. In the absence of rotation, an equilibrium poloidal field has recently been found for which there is no circulation. The present paper reports analogous equilibrium solutions for a star which is in uniform rotation.

The study of line-broadening mechanisms puts at our disposal an extremely useful tool for the investigation of physical conditions in plasmas, both stellar and laboratory.

When metre wavelength radars were first operated in the 1940s, echoes were obtained which could be attributed to backscatter from ionised trains produced by the ablation of meteroids in the upper atmosphere at altitudes near 100 km. Modern over-the-horizon skywave radars operating in the HF (High Frequency) band employ digital techniques for both radar control and signal processing and are aided by frequency management subsystems for the selection of appropriate frequencies for meteor detection based on real-time monitoring of the HF signal environment.

This paper describes the results of using such a radar for meteor observations. We report the detection of the Eta Aquarid meteor shower and demonstrate that a large increase in the echo rate due to sporadic meteors is obtained as frequencies are reduced below 15 MHz and the underdense echo ceiling rises in altitude. Finally, we present preliminary observations of highly Doppler shifted echoes which travel at meteoric velocities and which we identify as meteor ‘head echoes’.

Since the discovery of the first ‘head-tail’ radio source (Ryle and Windram, 1968) extensive radio surveys of clusters of galaxies have revealed a surprisingly diverse range of source morphology. In additions to the familiar symmetric double-lobed shape, several other morphological types are now recognised; these are presumed to be due to interaction between the source and a relatively dense, hot plasma pervading rich clusters. In particular, rapid motion of a radio galaxy with respect to this inter-galactic medium appears to produce a ‘bent-double’ shape, or in more severe cases, a ‘double-tail’ or ‘head-tail’ shape. In such cases, the source no longer has the simple symmetry of ‘ordinary’ double structure and it is clear that the attitude of the source with respect to the line of sight may markedly affect what is observed. Results and details are given below of a simple computer code used to simulate the appearance of a hypothetical bent-double source seen in projection. It is emphasised that the model has been chosen as one that can represent in a simple way many of the observed morphological forms and is not based on any physical theory of radiation or emission processes.

Since they were first interpreted, moving type IV bursts have been attributed to synchrotron radiation from electrons with energy ∼3 MeV radiating in weak magnetic fields (∼1 G) high in the solar corona. In this paper a description is given of 80 MHz radioheliograph observations of an outburst in which it was possible to isolate the moving type IV source and demonstrate that its circular polarization was strong (∼80%). Hence it is shown that the energy of the radiating electrons cannot exceed 6 = 105eV.

An albedo X-ray flux from the Earth was observed by experiments which were flown on Skylark rockets during April 1967. The details of the flights and the equipment have been covered in a previous paper. The celestial X-rays observed from discrete sources are superimposed on a diffuse X-ray flux. Most measurements of this diffuse flux have taken the difference between the number of X-rays observed from an area of sky, which is thought to be free of sources, and the flux from the direction of the Earth. By assuming that there are no X-rays from the direction of the Earth, this method removes the high-energy charged-particle background which should be the same in both cases.

The synthesis telescopes at Fleurs and Molonglo have been used to map 50 supernova remnants. Additional specialized software to process the maps has been developed, and Parkes observations have been used to supply short spacing information missing from the maps.

This review concentrates on observations of neutral hydrogen in the Magellanic System, and what they reveal about the structure, dynamics, evolution and ultimate fate of the LMC and SMC. Some recent observations of 161 Cepheid variables in the SMC are used together with the HI observations to determine the geometry of the SMC. These show that it has an amazing depth of at least 30 kpc. To explain the results it is proposed that the SMC had a close encounter with the LMC which has warped the disk of the LMC, produced the bridge between the two galaxies and tidally fissioned the SMC. The SMC is in the process of irreversible disintegration. It is believed that the Magellanic Clouds are not bound to our Galaxy and approached us from the direction of Andromeda. They may have had a close encounter with Andromeda 3 x 109 years ago, which may explain the massive starburst which occurred in the LMC and SMC at that time. It is believed that the Magellanic Stream has been swept out of the inter-Cloud region by the ram pressure of the gaseous halo of our Galaxy. If dynamic friction is sufficient for the Clouds to be captured and to eventually collide with our Galaxy, a polar ring will be formed similar to that observed in some other galaxies. The polar ring of dwarf spheroidals and outlying globular clusters at present encircling our Galaxy may be the remnants of a previous collision with some other galaxy 6 x 109 years ago.

This review surveys some recent observations of polarization in solar spectral lines with emphasis on their theoretical interpretation. Solar optical polarimetry is concerned primarily with measuring solar magnetic fields, a quest which began with Hale’s (1908) observation of Zeeman splitting in a sunspot. Today a wide range of optical polarimeters is used for solar research (see Bauer (1981) for a comprehensive review). For example, a standard magnetograph (Babcock 1953) detects circular polarization in selected wavelength bands in the wings of a Zeeman sensitive line, providing information on the line of sight or longitudinal field component. The most sophisticated instrument is a Stokes polarimeter (e.g. Bauer et al 1980, 1981) which measures with high spectral resolution the profiles of all four Stokes parameters (I,Q,U,V) across a spectral line. Such a device potentially provides all the data needed to infer the vector magnetic field.

Travelling disturbances in the solar corona with velocities ~103 km/s manifest themselves at radio frequencies by two distinctive phenomena—the type II burst, the spectrum of which shows a slow frequency drift that corresponds to quasi-radial outward motion, and the moving type IV burst, for which positional observations show transverse motion directly. A close relation between the two phenomena has long been suspected, and each type has separately been ascribed to a shock wave disturbance. In this paper we summarize three events recorded by the Culgoora radioheliograph and spectograph (two in the course of publication and one unpublished) in each of which a type II and a moving type IV burst can be consistently attributed to the effects of a common shock wave.