The extreme isotropy of cosmic ray events allows one to put upper limits on any possible non-isotropic contribution to the flux. In particular, one can investigate any excess of events which may be confined to the galactic plane. Such extra events would be expected from galactic ultra-high-energy (UHE) gamma-ray sources. Under the assumption of an isotropic cosmic ray flux, recent Buckland Park data place a 95% confidence level limit on the total southern hemisphere (declination −15° to −55°) flux of UHE gamma-rays at between 0.6 and 6 equivalent Cygnus X-3 sources, depending on assumptions concerning the gamma-ray spectrum.

The coalescence of two Langmuir waves, L and L′, produces emission at twice the plasma frequency in type II and type III solar radio bursts. The analysis of the coalescence process is usually simplified by assuming the head-on approximation, where the wavevectors of the coalescing waves satisfy kL ′ ≈ −kL , corresponding to the two Langmuir waves meeting head on. However, this is not always a valid approximation, particularly when the peak of the Langmuir spectrum lies at small wavenumbers, for narrow band spectra, and for spectra with broad angular ranges. Realistic Langmuir wave spectra are used to investigate the effects of relaxing the head-on approximation.

In the first four years of operation with the 80 MHz heliograph at Culgoora, 24 events classified as moving type IV were observed. Their observed characteristics can be interpreted in terms of gyro-synchrotron radiation from mildly relativistic electrons. Many of these events have been presented at previous ASA meetings and 12 have been discussed in the literature in detail.

A 30 MHz radio telescope has recently been completed at Fleurs, N.S.W. There has been a need for a high resolution sky survey to be carried out in the Southern Hemisphere at a frequency intermediate between 19.7 MHz (Shain et al.) and 85.7 MHz (Mills et al). One particular reason lies in the fact that some HII regions which are seen in absorption against the galactic background at 19.7 MHz and in emission at 85.7 MHz may match the background temperature at 30 MHz. If the temperature of such a region has been found by other means, the 30 MHz temperature of the portion of the Galaxy beyond it is determined irrespective of conditions nearer the observer, since the two temperatures must be equal.

The Japanese National Large Telescope is an 8-metre class optical-infrared reflector with a monolithic thin meniscus mirror, to be constructed at the Mauna Kea summit, Hawaii. The JNLT will be characterised by high quality performance in the optical and infrared regions, achieved by adopting new technologies such as active mirror support, fast optics and a thermally controlled dome. In particular, high infrared qualities are regarded as the most important characteristics among various design goals.

The JNLT project is now close to the final study phase before construction. This paper reviews the scientific motivations and the special technical features of the JNLT. Finally, the promotion of international collaboration around the JNLT is emphasised.

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.

Auckland Observatory is a public observatory with a strong research interest. Its activities are reviewed and described. The important role which public access to current astronomy plays is mentioned.

The M supergiants are rare objects in the solar neighbourhood and consequently until recently their importance has been largely overlooked. It is now being realized that these stars hold the key to extragalactic distance determinations since they can be detected at large distances while the maximum luminosity they attain seems to be remarkably constant and independent of galaxy type (Sandage and Tammann 1974; Humphreys 1978, 1979a, 1979b; Humphreys and Davidson 1979). They are also important in their own right since they are massive stars in the late stages of their evolution and undoubtedly suffer from mass loss and chemical enrichment due to the mixing of processed materials to their surfaces. In this light they can be considered as precursors of the luminous carbon stars and supernovae.

Radiation generated in the solar corona can be drastically altered by refraction and scattering as it escapes. This is especially true for sources having a frequency near the local plasma frequency, where the index of refraction approaches zero. Early investigations of the problem (e.g. Fokker 1965; Steinberg et al. 1971; Riddle 1972, 1974) have shown that the size, shape, location, intensity and time profile for the observed source can all be influenced.

A theory for the source of free energy for the Langmuir waves producing Type II bursts is presented. It is shown that electrons accelerated at the Type II shock naturally develop a distribution function with an abrupt cutoff at a characteristic minimum parallel velocity (a ‘cutoff distribution) in a limited spatial volume ahead of the shock, irrespective of the acceleration process active at the shock. The long duration, narrow bandwidth Type II radiation is then explained in terms of Langmuir waves produced by a cutoff distribution. The theory also accounts in a natural way for split-band Type II bursts and herringbone bursts.

The strategic value of infrared sensing has prompted military development — mostly in the USA — of detectors for 8-30 μm far more sensitive than any commercially available. In 1970-72 the Air Force Cambridge Research Laboratories conducted a rocket-borne survey of the sky N. of about -35° dec at 4,11 and 20 μm. Although this survey was initially classified, a small number of preliminary versions of it were distributed to selected infrared astronomers based at U.S. institutions.

There have been a number of attempts made in the last decade or two to observe deuterium in parts of the universe other than here in Earth. It is of interest merely to detect deuterium elsewhere just as it is to detect the occurrence of any nuclide. However in the case of deuterium there is a special interest because in big-bang cosmologies the great majority of deuterium in the universe is considered to have been formed in the initial fireball (Wagoner, 1973). Any observation of the present abundance of deuterium thus might give information about the very early stages of the creation of the universe. Detailed studies of nucleosynthesis during the early expansion of hot big-bang universes have however indicated a particular feature of deuterium production. (Fig. 1) The mass fraction produced X(D) is a very sensitive function of the size of the universe, as measured say by the present baryon density ϱb . Other nuclides that are mainly produced in the early expansion, such as 4He, have mass fractions less dependent on ϱb. Thus if we adopt the big-bang model for our universe we can determine ϱb from observations of X(D). Apart from any intrinsic interest in the present density of the’universe, there is considerable interest in whether the value is great enough for the present expansion to halt and go over to a collapse — or so small that the expansion of the universe will go on forever.

A grant from the Department of Employment, Education and Training and matching funding from the University of Western Sydney, Nepean, has allowed the construction of a teaching and public access observatory on the University’s Werrington North campus. The observatory consists of a lecture theatre for about 50 students, an office for administration and project/souvenir sales, and an enclosed office for research activities. The 6·5 m dome will house a fork-mounted 0·6 m (24 inch) Ritchey-Chrétien telescope working at f/10. There will also be two outside observation areas for tripod-mounted telescopes. The expected completion date for the entire project is mid-1994.

Millimetre-wave emission from the CO molecule has proven to be an extremely useful probe of the cold, dense clouds of molecular hydrogen in the Galaxy. Previous studies of the large-scale distribution of CO in the galactic plane (Scoville and Solomon 1975; Burton et al. 1975; Bash and Peters 1976; Burton and Gordon 1978; Solomon et al. 1979b; Cohen et al. 1980) have all been of the northern hemisphere and primarily at longitudes 0° ≤ l ≥ 80°. These studies have revealed the striking characteristic that the CO, and by implication molecular hydrogen clouds, are concentrated in a ring extending from 4 to 8 kpc from the galactic centre. This is in sharp contrast to the atomic hydrogen distribution, which is fairly constant over the extended region from 4 to 13 kpc but correlates well with other Population I indicators.

The Molonglo Observatory synthesis telescope (MOST) of the University of Sydney (Mills 1981) produces maps of the 843 MHz continuum emission from fields of width 23′, 46′ or 70′ arc. The telescope comprises two co-linear east-west cylindrical paraboloids each 2186λ in length and separated by a gap of 43λ. For each paraboloid a phasing network (Durdin et al. 1984) generates a comb of 64 contiguous fan beams. Mapping is accomplished in real time during a 12-h observation by overlaying, in the map plane, the instantaneous cross-correlations of corresponding beams. The synthesized point-source response (beam) produced by this method has a width of 43″ (E-W) by 43″ cosec δ (N-S).

Here we present our first results of a study of the neutral hydrogen gas (HI) in the southern spiral galaxy NGC 253 with the Australia Telescope Compact Array. The relative proximity of NGC 253 makes it a very suitable object for detailed studies of large-scale, as well as nuclear, gas dynamics. Several peculiar features have been found. The HI distribution is asymmetric in the outer regions, probably as a result of the strong warping of the spiral arms. A bar associated with the disc, clearly visible in the optical and near-infrared, also reveals its signature in the neutral hydrogen gas. HI absorption measurements reveal unusual motions of the gas in the nuclear region which seem to indicate a fast-rotating ring of cold gas as well as outflow of gas. Similar features have been found in other starburst galaxies, such as M 82, NGC 1808 and NGC 4945, and are interpreted in terms of bar-induced gas dynamics and star formation.