Gamma-ray astronomy has traditionally been a difficult field of research due to the low fluxes from astronomical objects and the inherently poor angular response of detectors. Progress made in the field in the last twenty years is reviewed. Many major astrophysical problems can only be addressed with the future operation of more sensitive satellite experiments. Recent gamma-ray observations of the supernova SN1987 a are briefly discussed.

A Hα flare (12°N., 49°W.) on 1968 August 23d23h45m was followed by a short-lived type II burst whose dynamic spectrum, as recorded with the Culgoora radio-spectrograph, is shown in Figure 1. The type II burst had split-band structure; the upper band drifted from 130 MHz to 80 MHz, the lower band from 100 MHz to below 80 MHz (at the time the 25-74 MHz band of the spectrograph was less sensitive than the 74-220 MHz). Unusual spectral features can be seen in each split band. The most remarkable one is an absorption feature between 23h52m02s and 23h52m 10s – the depression in the bright type II emission along an ‘inverted U’ (between 120 and 85 MHz). Several other similar, though less marked, absorption features can be found between 23h51m45s and 23h52m30s.

During the second half of the nineteenth century Australian amateur and professional astronomers worked together in actively promoting astronomy among the general public. This collaboration was a product of the cordial amateur-professional relations that permeated pre-astrophysics Australian astronomy.

To date the Culgoora radioheliograph has recorded seven continuum bursts simultaneously at its three operating frequencies of 160, 80 and 43 MHz. In every case the radio emission is found to originate from stationary sources whose heights increase with decreasing frequency. The implications of these new observations are discussed below.

Two outstanding problems in the interpretation of OH masers are their narrow linewidths, and the rare occurrence of Zeeman pairs (Reid and Moran 1981). On discovery, the narrow but intense features of OH sources suggested unsaturated maser action (Perkins et al 1966). However the features are often so bright that saturation must be involved, and in saturated growth the features should rebroaden to about the thermal width (Goldreich and Kwan 1974). This is not observed (Reid and Moran 1981).

Although the gap between the observational data from northern and southern hemisphere started recently to narrow, the long neglected southern hemisphere is still far behind the northern. I have especially in mind binary and variable stars. The systematic research in this field in the south is not satisfactory and many interesting objects still await to be properly observed and many to be discovered. We are now grateful to our predecessors who 70 years ago started the photographic patorl of northern sky so that we are now able to trace back the behaviour of many interesting objects such as X-ray sources; we may follow back the changes of light curves and derive important conclusions from the changes of periods.

There have been extensive calculations of model atmospheres of stars over the past few decades. Almost all of these calculations have assumed radiative equilibrium. Except for convection, very little work has been done on the stability of the surface layers of stars at small optical depths. Although there has been a considerable amount of research concerning the stability of stars, this work has assumed the diffusion approximation for the transport of radiation and has been primarily concerned with the envelopes of stars rather than their atmospheres.

We present broadband photoelectric light curves for the RS CVn type star PZ Telescopium for 1980, 1982 and 1983. The photometric period is about 0.943 days. The V light curve shows radical changes in form and range over a few months, and may be continuously variable. B and V data were obtained in 1982 and 1983. In 1982 no (B-V) change with phase was detected. However, in the first part of the 1983 observing season, a (BV) change of around 0.02 magnitude was found. Also at this time, maximum light was some 0.05 magnitude above that measured previously. Our preliminary spectroscopic data obtained in 1983 indicate that PZ Tel is a double lined binary whose components are of approximately equal luminosities, but this is yet to be confirmed. We suggest that the photometric variations are due to the presence of large cooler starspots on the photosphere of one or both components, as seems to be the case for related systems. The rapid changes in the observed light curve imply equally rapid changes in the distribution of the starspots, and make this an interesting object for further study.

Visual meteors, due to impinging meteoroids of radius about 1 cm, appear at a rate of a few per hour during non-shower periods. Smaller meteoroids (100 μm – 1 cm) give rise to less bright trails, but are much more abundant. These are usually detected by radars of about 10 m wavelength which, over the past 40 years, have produced a plethora of information concerning mass and height distributions, orbits, etc.

Using such ‘conventional radars’, the peak of the measured height distribution is found at about 95 km, with few meteors detected above 105 km. However, the flux detected is only a few percent of the total flux (a) measured using a large (10 m) optical collector, and (b) expected from a comparison with measurements by satellite impacts and zodiacal light observations (radii < 100 μm). One possibility is that the radars detect few low-velocity (V < ~25 km s-1) meteors since these produce little ionization and thus limit their detectability: the ionizing efficiency of meteors varies as ~ V 7/2. In direct opposition, our alternative hypothesis is that the undetected flux is held in a faint high-velocity component which ablates at high altitude. These are not detected by conventional radars because meteor trails have ‘initial widths’ of about 3 m at 105 km; for a radar wavelength of 10 m, components scattered from different regions of the trail therefore destructively interfere, and the probability of detecting any meteor above 105 km is small.

In order to test our hypothesis we have measured the height distribution with a 150 m radar, and we are commencing ancillary observations at 50 m; compared to these wavelengths the initial width is small to at least 140 km. The results show a peak at 105 km with most meteors being above this, significant numbers occurring right up to 140 km. This suggests that the true flux is at least 10 or 20 times that previously deduced, having implications for the number of cornets in the recent past and the balance of material between the smaller bodies in the solar System.

The object of this contribution is to report the galactic background intensity at 2 and 3 MHz. The observation is an extension of earlier work which the noise temperatures at 50, 30, 20, 10 and 5 MHz were obtained at 65°N declination by means of identical antennas of beamwidth 70° between half-power points. As discussed in the earlier work, the temperatures were obtained separately in the ordinary and extraordinary modes, in order to account for the attenuation in the ionosphere.

We have discovered a radiation levitation mechanism which, under certain circumstances, can remove the last vestiges of hydrogen-rich material from an incipient planetary nebula nucleus if its mass exceeds a critical value of about 0.85M⊙. This process may be responsible for the production of helium-rich planetary nuclei, and their progeny the DB white dwarfs.

The theory of neutron star formation is addressed in the light of the detected neutrino burst from SN 1987A. A brief review of how supernova neutrino theory has evolved over the last 30 years and a general analysis of the SN 1987A detections is presented.

In his studies of the temperature fluctuation in the solar photosphere P. R. Wilson came to the conclusion that, in order to explain Edmond’s r.m.s. intensity fluctuation distribution against heliocentric angle, one is led, using two dimensional solutions for the equation of radiative transfer, to the existence of a sharp temperature fluctuation of about 660 K r.m.s. at a depth of 250 km below τ5000 = 0.03 and that this temperature fluctuation decreases sharply in the next 70 km. There also seems to be an indication that there exists a second temperature fluctuation maximum at a depth of approximately 100 km below the first one.

The heights of solar radio sources at 1424 MHz and 696 MHz have been measured during the years 1965 and 1966. Solar activity at this time was near minimum. The number of radio sources appearing on the solar disk rarely exceeded three at any time and it thus was possible to resolve the majority of these with a high resolution grating interferometer. Many of the previous height measurements at these frequencies have been made near times of maximum solar activity and the confusion of sources within the beam has limited their accuracy. The number of sources studied here is quite considerably higher than in any previous investigation at these frequencies, and the period of observation has been continuous.

We have carried out a survey of the 115 GHz CO emission (J = 1→0 transition) towards the Carina nebula (NGC 3372) using the Epping 4 m radio telescope of the CSIRO Division of Radiophysics. Of all the molecules detected in the interstellar medium CO is perhaps the best tracer of molecular clouds. It is an abundant molecule (second only to H2) and its line emission at microwave frequencies occurs at relatively low excitation.

A program has been designed for Hewlett-Packard 9100 A Calculator connected by a 9102A Buffer to a 9101 A Extended Memory, a 9120 A Printer and 9125 Plotter. The program evaluates and plots one-night photoelectric measurements in 3 colours of a short period eclipsing variable and detects the exact time of the minimum. The program may take a maximum of 24 observations either of a comparison star or of the variable in each colour but it could easily be modified for a maximum of 36 observations in two colours or seventy two observations in one colour. The usual alternating succession of the type CVCVC… is supposed but up to three successive measurements both of the comparison star and of the variable is possible, e.g. CVCCCVCVCVVVCVC…