The study of radio galaxies situated within clusters of galaxies has become a broad field, with hundreds of papers published in the last few years. This review will therefore be restricted mainly to consideration of the interactions between the extended components of radio sources in clusters and the diffuse gas (intracluster medium, ICM) which occurs in clusters. In particular, attention will be focused on what we can learn about the ICM from this interaction, in conjunction with other data such as X-ray observations. In the case of quasars in clusters of galaxies the emphasis is rather different, so discussion of this topic is deferred to section 6.

We demonstrate the presence of a cluster of hot, population I stars at the very centre of the Galaxy, using the depth of the first overtone band of CO and the presence of emission in He I 2 ·058 μm and [Fell] 1·644μm to identify stars. The cluster is very compact and comprises at least several hundred stars. They lie close to the nonthermal radio source Sgr A* and dominate the luminosity and mass loss of the Galactic core. Their presence suggests that a starburst occurred at the Galactic centre.

A great deal has been learnt about supernovae over the last 500 days, or so. The major deficiencies in theory highlighted by the case of SN 1987A are briefly reviewed, as are the sucesses.

We present observations made at 80 MHz with the Culgoora radioheliograph of the compact central components of the radio source Centaurus A, which is associated with the peculiar galaxy NGC 5128.

The ratio of the mass density in visible galaxies to the upper limit for the HI mass density determined from the lack of continuous Ly-α absorption in QSO spectra is 3 × 104. Thus, if galaxies form by condensation from an intergalactic medium, the process must be extremely efficient. Although no absorption due to a continuous distribution of intergalactic HI has been detected, many QSOs have been discovered that have absorption lines in their spectra, which have redshifts very different from the emission lines, and may be produced in clouds of integalactic HI. As would be expected if this were the case, the proportion of QSOs with absorption lines in their spectra is greatest for those which have large emission line redshifts. Another possibility, especially for those absorption lines in redshift systems with Z abs nearly equal to Z em , is that the absorption lines are produced in clouds surrounding the QSO.

In 1983 ultra high energy γ-rays were detected from Cygnus X-3. This was of particular interest since it is the first identifiable source of cosmic rays. Since then, there has been an explosion of interest in the field with more than twenty air shower arrays planned or being used to search for γ-rays at energies above 1014 eV. Observational techniques for both very high energy and ultra high energy γ-ray astronomy are described and existing and proposed experiments reviewed with particular reference to their geographical locations. The results obtained so far are summarised together with some of the models proposed to explain them.

In a technical sense radio astronomers do not use the radio spectrum; they are listeners only, and when the science began they had to listen in the quiet spaces between transmitting services. Radio astronomy was first recognized as a service by the International Telecommunications Union (ITU) in 1959, and the first frequency allocations were then made for it as a ‘passive’ service. In 1963 and 1971 further allocations and frequency protection were obtained at specialized World Administrative Radio Conferences (WARC). The allocations were required for two purposes: (i) to protect the frequencies of the most important spectral lines of atoms and molecules, and (ii) to provide a series of bands for continuum observations. The general protection so far provided has been vital to the growth of the science, and its continuation is of the highest priority to the future life and development of radio astronomy.

It has recently been reported (Cini-Castagnoli et al. 1973; Jacklyn and Cini-Castagnoli, 1974) that Jupiter may be responsible for a modulation component in the counting rate of underground cosmic ray detectors on the earth. The evidence suggests that a screening mechanism is operating, in as much as the observed counting rates are diminished when Jupiter is within the field of view of these detectors. The magnitude of the effect is larger than can be accounted for by simple line-of-sight obscuration by the planet itself, and it has been suggested that the intense and extensive Jovian magnetic field is producing the effect.

Observations of the solar surface indicate a cellular structure, photospheric granulation, which, as suggested by Wilson and others, could arise from a shallow convection layer. The basic observed granulation pattern has been likened to a hexagonal cell type structure.

We present the results of spectral observations on Nova Vulpeculae (1) 1984 (RA = 19h24m, Dec = 27° 15′), taken on 1984 August 21 (JD 2445934.4) and 1984 August 31 (JD 2445944.4). The data obtained gives additional information on the nova’s spectral evolution presented by Andrillat and Houziaux (1985), filling the gap in their observations.

Cen X-3 and Her X-1 are the only two X-ray binaries which are known to pulsate periodically (at 4.8s and 1.2s respectively) in the X-ray region. The latter was identified with a fourteenth magnitude light and spectrum variable HZ Her, which was subsequently found to exhibit 1.24 second optical pulsations during certain phases. The possibility that Cen X-3 may prove to be as interesting an object optically has resulted in a wide spread search for its optical counterpart.

The disk stellar luminosity function has been redetermined by the mean absolute magnitude method, utilising the proper motion data of the LHS Catalog. The derived luminosity function shows a slightly deeper dip than that found by Wielen (1983) in the same magnitude range.

The Chatterton Astronomy Department of Sydney University, in collaboration with the Astronomy Group of Imperial College (London), has carried out a program of speckle interferometry on the 3.9 m Anglo-Australian Telescope (AAT). Over 2 km of film were exposed during the two observing sessions in November and December, 1978, and the analysis of this very large amount of data is being carried out at the present time.

The arms in spiral galaxies cannot be material arms for then they would wind up on a time scale of one galactic rotation, or a few times 108 years. The large number of spirals suggests that the spiral pattern must persist for about 1010 years (or be continually rejuvenated). The density wave theory treats the spiral pattern as a wave phenomenon, thus overcoming this problem. Much work has been done studying small amplitude oscillations in flat stellar discs. Self-consistent spiral modes have been found, but they are not stable and grow at a fast rate. Numerical simulations of thin stellar discs, such as those of Hohl (1971), which can handle finite amplitude waves, have been more successful. Spiral waves form initially but evolve into a steady state rotating bar. It seems therefore, that a long-lived spiral cannot be formed in stars alone.

There is reasonably strong evidence to suggest that the periodic X-ray, radio and optical variable Cir X-1 is a highly eccentric orbit (e ~ 0.8), binary system comprising an OB supergiant primary and a compact object, probably a neutron star (Whelan et al. 1977; Haynes, Lerche and Murdin 1980).

Large outbursts from the Sun which are widely extended over centimetre and decimetre ranges and show smooth time variations in intensity have been called microwave type IV bursts (μ-IV). Those bursts generally consist of more than two successive components, the spectra of which move progressively towards the lower frequencies. Furthermore there is a tendency for the decay times, which are defined as the times occupied by the decreasing parts of the bursts, to become successively longer. It seems worth while to make a quantitative study of the time variation of the decay times and flux densities of μ-IV burst spectra and to infer how the physical conditions in the source change with time.

This paper presents results from speckle observations of binary stars carried out between 1987 and 1990 using a 212-cm telescope at the San Pedro Martir Observatory, Mexico.