It was first shown by von Zeipel (1924) that strict radiative equilibrium is impossible in the radiative zones of a uniformly rotating star. This result lead Eddington (1925) and Vogt (1925) to independently suggest the existence of large-scale meridional currents in the radiative zones of rotating stars. Eddington argued that since these currents will transport angular momentum, the condition of strict radiative equilibrium would result in meridional currents combined with differential rotation.

We are studying the distribution and morphology of magnetic fields in southern face-on and edge-on galaxies with the intention of clarifying the distribution, lifetimes and transport mechanisms of cosmic rays, and investigating the intensity and orientation of the disc, halo and poloidal magnetic fields. As a preliminary study, before the Australia Telescope was available, we observed a sample of well-known southern spiral galaxies with the Parkes radio telescope.

Here, we present the resulting polarisation images for three galaxies, NGC 253, M 83 and NGC 4945, which were observed at 4.75 GHz and 8.55 GHz. The corresponding total power contour plots have been already published by Harnett et al. (1989a, 1990).

During the period 1966 July 12 to August 5 observations were made of the Sun at three radio observatories. The instruments used were the east-west arm of the Mills cross at Molonglo (408 MHz) and the Christiansen cross at Fleurs (696 MHz and 1424 MHz). The aim of these observations was to study the discrete sources of the slowly varying component of solar radio emission, while activity was comparatively quiet. The three frequencies enabled the variation of source structure with height of solar atmosphere to be studied. It has been pointed out by Swarup et al., and Christiansen et al. that the determination of the frequency dependence of these discrete sources is important for defining the physical mechanisms causing the radio emission.

The Australia Telescope Compact Array has been used for observations, with arcsecond resolution, of the HII region N159 in the Large Magellanic Cloud. Images at 5 GHz reveal a second compact continuum component which has no obvious counterpart at optical and infrared wavelengths. Observations of HI 10α recombination-line emission, and HI and H2CO absorption, suggest that the object is a compact HII region embedded in a dense obscuring cloud on the edge of N159.

Worm-gear drives for astronomical telescopes have associated with them certain requirements which cannot be effectively dealt with by applying standard design methods and parameters, since these drives differ in many ways from conventional power transmission gearing.

Pulsars display a complicated pattern of amplitude variations. The scale of variations range from months through hours to sub-milliseconds. The purpose of this note is to present polarization data for CP 1919 and intensity distribution data for PSR 0833—45 which are relevant to pulse-to-pulse variations and the variation over periods of hours respectively.

The satellites of the outer solar system appear to be composed principally of water ice and silicates, with the presence of ammonia and methane hydrates (Lewis 1971). Although these bodies are small (with radii typically < 1000 km) they can exhibit very active evolutionary histories, due to the low melting point of water ice.

Expressions for the physical structure of a sequence of two zone polytropic stellar models, based on composite analytical solutions of the Lane-Emden equation with indices n = 1 and n = 5, hâve been determined. The coefficients of vibrational stability for radial oscillations of this sequence of models have also been calculated and it is found that increasing the extent of the n = 5 outer zone has a stabilizing effect.

Low frequency radio waves propagating in the interstellar medium are attenuated through absorption by thermal electrons, the optical depth being given by

where f is the radio frequency in MHz, the emission measure in cm-6 pc, and Te the electron temperature.

A broad-band (2-190 keV) Australian X-ray satellite could provide a spectral sensitivity substantially better than HEAO-1 or any presently approved spacecraft. It would be virtually unique by providing simultaneously data over a wide energy range with high sensitivity and energy resolution in the little measured region above 30 keV. These measurements are vital to our understanding of such diverse topics as the cyclotron line production mechanism in binary sources, the structure of the magnetosphere of neutron stars, the origin of the diffuse cosmic X-ray background and the nature of the giant power sources in active galaxies and stellar black holes. Details of the proposed spacecraft and scientific objectives are given.

Fabry-Perot instruments have been extensively used for many years for the study of spatially extended emission nebulae because they offer a potential luminosity resolution product (L × R pot) which exceeds by a high factor tha attainable by aerating spectrometer. Meaburn (1970) shows that this product is given by the relationwhere P is the number of resolution elements each containing a maximum solid angle, Ω observed simultaneously, ti is the refractive index of the medium between the plates, A is the acceptance area of the device, εo is the transmission coefficient of the associated optics and εF the transmission coefficient of the Fabry-Perot (which if coated with dielectric multilayers can be very high).

Observations on 1970 August 11 and 12 at Mauna Loa (Hawaii) of the white-light corona revealed a rare solar event in the form of a short-lived coronal brightening off the eastern limb of the Sun. The intensity of this region, as measured at a distance ρ = 1.5 (where ρ = R/R⊙), more than doubled over a period of five hours and then fell very abruptly (~10 min) to below its initial brightness. A complex radio event in the same region was observed simultaneously with the 80 MHz radioheliograph at Culgoora (Australia). Associations between the optical and radio events will be described and the physical implications briefly discussed.

During the solar maximum of 1989–91 an unprecedented sequence of 13 cosmic ray ground-level enhancements (GLEs) was observed by the world-wide neutron monitor network. Of particular interest were two GLEs observed by the Australian network. The 1989 September 29 event was the largest GLE in the space era while the October 22 GLE included an highly anisotropic precursor peak.

Analysis of both these GLEs, taking into account disturbed geomagnetic conditions, shows that the particle arrivals at the earth were unusual. The September 29 GLE had significant particle propagation in the reverse direction and as the particle flux decreased following the peak the spectrum also softened. In contrast, the 1989 October 22 precursor exhibited extreme anisotropy while the particles involved in the main GLE showed a complex temporal structure possibly indicating multiple particle injection at the solar acceleration region.

New radio and optical telescopes installed in recent years in China are summarised. These include the 2.16-m optical telescope, the solar magnetic field telescope, the Miyun synthesis radio telescope, the 1.26-m infrared telescope (Beijing Astronomical Observatory), the 25-m radio telescope as the first station of China’s VLBI network, the 1.56-m astrometric telescope (Shanghai Observatory), and the 13.7-m millimetre wave radio telescope.

The research now under way with the real-time 275 km Parkes-Tidbinbila interferometer is used as a guide to the initial science to be undertaken with the 319 km Australia Telescope (AT) Long Baseline Array. On the other hand, it is risky to guess at the new science likely to be attempted with the 6 km AT Compact Array at Culgoora; instead the potential that has been built into this array is discussed and a selection of basic questions in astrophysics is posed as a guide to significant science that might yield to new observers on a fresh instrument under the southern skies. In conclusion two questions are probed: Can discoveries be made by users of national facilities? Does the AT cross into new domains in the phase space of observations?

This cluster has two notable characteristics: it contains more than 80 variables, and relative to its NP half its SF half is covered by a cloud absorbing up to a magnitude in the blue. These properties make it an ideal object for determining the ratio Av/E of V absorption to colour excess—one simply compares mean colours and magnitudes of variables in the obscured part with those in the clear part.

One of the major problems in the theory of type III solar radio bursts concerns the development of the two-stream instability. On the one hand, Sturrock (1964) argued that one expects the instability to develop rapidly, and if it does it should prevent the stream from propagating through the corona, contrary to observation. On the other hand, one appears to require that the instability develop partially, in the sense that there is some significant amplified emission of Langmuir waves, in order to account for the observed emission.