As part of an investigation of solar radio bursts at high time (≈ 1 msec) and frequency (≈ 10 kHz) resolution, observations have been made between 30 MHz with the Llanherne broadband radio telescope (Ferris 1980). The radio frequency signals in the six frequency ranges 30-33, 33-36, 38-41, 54-57 and 79-82 MHz were recorded on six video tape recorders for about 10 minutes each day near solar transit.

Ground-based observations of Jupiter’s decametric radio emission (DAM) have been reviewed by Ellis (1965), Warwick (1967, 1970) and Carr and Gulkis (1969). A startling feature of DAM is the modulating effect of Io, and interpretation of the Io effect has dominated theoretical discussions of DAM until quite recently, specifically until the fly-by s of Voyagers 1 and 2. The Voyager data showed that the DAM appears as nested arcs in the frequency-Jovian longitude plane (Warwick et al. 1979, Boischot et al. 1981). The interpretation of this arc structure has been of primary theoretical interest over the past two years. The most widely adopted explanation is that the emission from each point is confined to the surface of a hollow cone (Goldstein and Thieman 1981). This idea is not new: emission on the surface of a cone was discussed by Ellis and McCulloch (1963); Dulk (1967) derived detailed parameters for the cone (half angle 79° width 1°) from the occurrence pattern of DAM; and Goldreich and Lynden-Bell (1969) presented a theoretical interpretation of it. More recently Goldstein et al. (1979) used observational data on the Jovian magnetic field in deriving properties of the required emission cone. It seems that one requires the properties of the emission cone to vary with position in the Jovian magnetosphere to account for the nested arc pattern (Goldstein and Thieman 1981; Gurnett and Goertz 1981).

The term ‘moving Type IV’ denotes a spectacular class of solar event in which the radio source, beginning low in the corona, moves outward, typically at hundreds of kilometres per second (Wild et al. 1963).

An accurate determination of the global Hubble Constant needs distance to objects well outside the Local Supercluster with redshift greater than ~ 2000 km/s. This is mainly to reduce the effect of the peculiar motion of the Local Group on the measured redshifts as well as to get away from the gravitational influence of the nearby high density regions.

The present practice of deriving distances involves identifying objects such as Cepheids and brightest red stars both in the Local Group galaxies as well as in the distant galaxies. This method cannot be used for galaxies at the large distances.

Flux density changes at low frequency in extragalactic sources were discovered in 1969 by Hunstead (1972a) and this low frequency variability has since been confirmed in the range 318 to 962 MHz at five other observatories. The changes are usually small and near the stability limit of most telescopes, but occasionally large changes ~ 30% are found. Many sources show changes at both low and high frequencies, but these appear uncorrelated even with delay lags of several years, and the likelihood of low frequency variability in a source cannot be predicted from high frequency behaviour. This paper reports statistics on the proportion of sources that showed changes of different amplitudes during a monitoring program with the Molonglo Cross in 1975/76.

The aim of this study is to investigate the spheroidal halo around our Galaxy, that is, the outer extentions of the central bulge. The kinematics and variations in metal abundance in the halo are important astrophysical parameters for any theory which models the formation and evolution of our galaxy. Attempts to determine these parameters have so far used a particular class of stars which can be easily identified as members of the halo.

The aggregation of a large number of planetesimals into a single body is a problem that has proved to be a stumbling block for many theories of planetary formation. This difficulty has mainly arisen because of the tendency of an orbiting stream of bodies to disperse over the equatorial plane as a result of the combined effects of collisions and gravitational interactions (Trulsen 1972; Brahic 1975). Once such a chaotic distribution of orbiting bodies has developed, it is extremely difficult for these bodies to subsequently accumulate into a single entity. This problem does not arise, however, when aggregation takes place within a differentially rotating gaseous ring as proposed by Prentice (1978). It has been shown previously (Hourigan 1977) that the gas drag overcomes the disruptive nature of collisional interactions, resulting in the formation of a thin concentrated torus of orbiting bodies.

The soft X-ray source HO 139-68 was originally detected with the low energy detectors of the HEAO A-2 experiment, and confirmed by later IPC observations (Agarwal et al. 1981). The X-ray observations show flux variations in the 0.15 – 0.4 keV band of a factor of two, or timescales of a few hours, with evidence for short time-scale flickering. Following communication of the source position to us by Agarwal and Riegler, we obtained time-resolved optical spectrophotometry of a star close to the X-ray position, using the IDPCA on the MSO 1.9m telescope. The spectrophotometry and later polarisation observations confirm the optical identification and that the source is an AM-Herculis type binary system, with a late type dwarf secondary overflowing its Roche lobe in a magnetically constrained funnel onto a magnetic white dwarf (WD) primary (Visvanathan and Pickles 1982).

The discrepancy between the observed and predicted flux of neutrinos from the Sun is well known. Past attempts at reconciling this difference have been unconvincing (Kuchowicz 1976, Rood 1978), and hence investigations in this area continue.

Radio measurements of the outer planets at wavelengths longer than ~ 10 cm are difficult: the emission is weak (generally following an optically thick thermal spectrum — i.e. S ∝ λ-2) and the confusion due to background sources may be large.

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.

We present 2.2 μm maps of four southern HII regions. Although each of these objects has been extensively studied at radio wavelengths with low spatial resolution, they have so far (with the exception of G333.6 – 0.2) received little attention in the infrared. As a first step towards understanding the structure of these objects we have therefore produced images of each in the K-band (2.2 μm) continuum.

Solar metre-wave noise storms commonly show continuum and short-lived narrow-band bursts (Type I) at high frequencies and fast-drift bursts (Type III) at low frequencies (Malville 1962; Hanasz 1966; Boischot et al. 1970; Moller-Pedersen 1974; see also Figs. 2-3 of this paper). The Type I and Type III emissions have the same sense of polarization (Komesaroff 1958; Suzuki 1978). Impressed by this spectral association, Malville (1962) and Boischot et al. (1970) suggested that the two types of emission might be excited by the same electron stream. However, Type I emission is associated with sunspots and strong photospheric magnetic fields (McCready et al. 1947; Payne-Scott and Little 1951; Le Squeren 1963) and for this reason Kai (1970) suggested that Type I emission arises on strong closed magnetic loops. Type III emission, by contrast, almost certainly arises on open or quasi-open (large-loop) magnetic field lines (Wild et al. 1959, 1963). Thus on these models one would expect Type I and Type III emissions to arise from different magnetic regimes and different areas of the Sun. Kai’s (1970) and Stewart and Labrum’s (1972) Culgoora radioheliograph observations, which suggested that Type I and Type III sources are always separated on the Sun, seemed to clinch the matter. Kai’s model and his statement ‘Type III sources avoid the precise location of Type I storm centres’ gained wide acceptance (e.g. Boischot et al. 1971; Elgaroy 1977; Stewart 1977).

There has been considerable speculation in recent years about the evolution of radio galaxies in clusters. The discovery of powerful X-ray emission with an apparently thermal spectrum from a considerable number of clusters has been attributed to a hot (108K) intracluster gas with an electron density of ∼ 10-3 cm -3 at the cluster centre (see e.g. McHardy 1978). Such a gas surrounding a radio galaxy may conceivably retard the expansion or diffusion of the relativistic electrons and thus allow the source to retain its identity for longer intervals than is the case for field galaxies.

The origin of QSO redshifts is an important problem for which there is still no definite answer (Burbidge 1979). Recent observations by Walsh et al. (1979) of what is probably a gravitational lens associated with the twin QSO’s 0957+ 561 A,B offers the possibility of testing whether the redshift of the QSO involved is cosmological in origin. In general, if a gravitational lens is responsible for splitting the image of a QSO into two or more distinct components, it is possible to calculate the redshift of the QSO provided we have enough observational data involving the lens. The calculated redshift must then be consistent with the observed redshift if it is entirely cosmological in origin. The quantities that must be observed before the redshift can be calculated are the differences in the light travel times along the different paths from the QSO to us, the redshift of the lens, the angular separation of the images, and their relative intensities.

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).

The 4-m radio telescope of the CSIRO Division of Radiophysics at Epping is being used to survey the line emission associated with the 1→0 transition of CO (rest frequency 115.271 GHz) in the southern Milky Way. The programme includes mapping the CO distribution across giant molecular-cloud/HII-region complexes. As a first stage the emission has been observed towards bright southern HII regions. These results will not only serve as a basis for future extensive mapping but will also provide data which is directly comparable with observations of other molecular lines that have been made towards the HII regions.

Most of the galaxy redshifts currently available in the literature have been measured from photographic spectra and are generally based on subjective estimates of the position of the narrow absorption features. In using only the few prominent absorption lines, most of the light from the galaxy is discarded. With the advent of digital linear-response detectors it is possible to obtain accurate and objective redshifts by cross-correlating all or part of the galaxy spectrum with a template galaxy of known redshift (Tonry and Davis 1979, Kelton 1980 and references therein).

In the terrestrial environment the abundance ratio of 18O to the common oxygen isotope 16O is about 1 in 490. Measurements of hydroxyl absorption in the interstellar medium show that 18OH as well as 16OH can be detected towards Sgr A and Sgr B2 (Gardner et al. 1970; Wilson and Barrett 1970; Williams and Gardner 1981); in these two galactic centre regions the 18OH isotopic species has an abundance relative to 16OH of about 1 in 220, somewhat greater than the terrestrial ratio of 18O to 16O.

Lynds 1642 is a small, somewhat insignificant dark cloud centred at 04h33, — 14°20 (1950). On a IIIaJ UKSTU Schmidt plate it may be seen to lie within an approximately circular patch of nebulosity which we believe to be visible by reflection. Its galactic location (l = 210°.9 b = -36°.5) places it beneath the local arm in the direction of Orion and it is likely that it is seen by reflection of the integrated light of the stars in that region of the galaxy.