Many cold molecular clouds have been detected as a result of their association with dense optical obscuration. The HII region RCW 36 is contained within a prominent dust lane extending several degrees along a line of almost constant right ascension (see e.g. Rodgers et al. 1960). By means of H2CO and OH observations we have found that this lane is associated with a dense elongated molecular cloud.

The pulsar 0833-45 associated with the Vela supernova remnant has been known as a strong source with fairly constant pulse amplitude since its discovery (Large, Vaughan & Mills 1968) using the east-west arm of the Molonglo telescope. The pulse stability together with the short period of 89 ms allowed its integrated flux to be seen also as a 1.7 Jy point source with the pencil beam of the full Cross, and a more precise declination was obtained. Further observations in 1971/72 with a beat period integrator used on the fan beams of the north-south arm showed that the pulsed radiation had the same declination as the point source within 2 arcsec (Vaughan & McAdam 1973). Monitoring observations in 1975/76 gave an independent position, and the mean of all Molonglo (408 MHz), Fleurs (1415 MHz) and NRAO interferometer (2700 MHz) positions led to the optical detection of the pulsar (Goss et al. 1977). The point source, therefore, is reliably identified with the pulsar.

Although the radio continuum distribution of the HII-region/molecular-cloud complex W33 (peak l = 12°.8, b = -0°.2) resembles a discrete region about 15′ arc in size, the behaviour of the recombination-line velocities (Gardner et al. 1975; Bieging et al. 1978) and molecular-line velocities (OH: Robinson et al. 1970; H2CO: Gardner and Whiteoak 1972) has been difficult to interpret in terms of a simple model. There is a difference of opinion as to whether W33 consists of two independent complexes at different distances along the line of sight or a single expanding complex (e.g. Goss et al. 1978).

The existence of a group of magnetic white dwarfs with mean surface fields of between ~5 × 106 G and ~2 × 1O7 G is now firmly established through the discovery of Zeeman structure in hydrogen and helium lines (Angel et al. 1974, Liebert et al. 1975, Wickramasinghe et al. 1977, Martin & Wickramasinghe 1978, Liebert et al. 1977). There is considerable evidence from polarimetric studies for even higher fields in some white dwarfs (Angel 1977). Most of these stars are cool and show nearly continuous spectra or weak unidentified absorption features. The possibility of cyclotron absorption in white dwarfs was first discussed in connection with the infrared polarisation spectrum of one of these stars, Grw + 70°8247 (Kemp 1970). More recently the polarised white dwarf GD229 was found to have a rich optical spectrum with a strong feature at λ4185, for which cyclotron absorption has been mentioned as a possible origin (Angel 1977, Greenstein & Boksenberg 1977), though without supporting computations. In this letter we use models to investigate this possibility further.

The radio emission associated with SN 1987A appears to be synchrotron emission resulting from the acceleration of electrons at the interface between the outward moving shock wave and clumps of circumstellar material. The Australia Telescope Compact Array is now able to resolve this region, which has dimensions of ~ arcsec, revealing a slight (10%) asphericity in the distribution of the low density gas within the [OIII] circumstellar ring. Assuming that the radio emission arises from a region just behind the shock front, we deduce a mean radial expansion velocity, from 1987 to 1992, of 29 200 kms. First observed contact of the shock with the [OIII] circumstellar ring could occur as early as mid-1993, depending on the deceleration in the intervening gas. This will probably be closely followed by shock-excited optical lines, a strong X-ray outburst and a further increase in the radio emission.

There are three non-thermal sources in the Large Magellanic Cloud which are recognized as supernova remnants. They are N49, N63A and N132D in Henize’s catalogue; a summary of their observing history is given by Westerlund and Mathewson (hereinafter referred to as ‘WM’). They are rather important to our knowledge of supernovae, as there are only four galactic supernova remnants (Cas A, the Crab, the Cygnus Loop and Vela) whose distances are known approximately from independent evidence. Since the distance to the LMC is well-known, the distance to sources in it is also known quite accurately.

The influence of the progenitor’s stellar wind on the supernova event, and subsequent development of a remnant are discussed. Various morphological differences between SN remnants and the implications for previous wind activity are described. A detailed look at the effects in the ring nebula NGC 6888 is presented.

Many authors (e.g. Magun et al. 1975) have debated the question ‘does solar type IV continuum emission arise through Langmuir wave conversion or through gyro-synchrotron emission?’ Culgoora radio spectrograph and heliograph observations of the late stages of a recent (7 September 1977) type II, IV event showed both type IV* (continuum) and transient type III (electron-beam) emission coming from the same source, high above the solar limb. These observations suggest that this particular type IV continuum arose through a mechanism similar to that of the type III, probably fundamental Langmuir-wave emission, in a corona with a tenfold enhancement of plasma density.

The thermal emission from a cold, dense molecular cloud peaks in the far IR, and the spectrum is rich in molecular lines in the submillimetre and millimetre bands. Observation of these bands is hindered, however, by atmospheric water vapour, which absorbs the incoming radiation. Ground-based mm observations from Australia, where the atmospheric water vapour content typically contains ~10 mm precipitable (ppt) H2O, can only probe a few of the molecular transitions from the heavier molecules, such as CO, CS, HCO+ and HCN. Sub-mm observations would enable the higher rotational lines from many of these molecules to be studied, and open up other spectral features to scrutiny, such as the lines from hydrides (e.g. CaH, NH, SH) and neutral carbon at 370 and 610 μm. However, they cannot be made from Australia. While sites such as Mauna Kea, which has ~1 mm ppt H2O on the best days, open the sub-mm band to partial viewing, their utility is limited in comparison to the opportunities possible from the Antarctic Plateau. Here the column of H2O drops to 100–250 μm.

A natural introduction to this topic is a brief discussion of two phenomena observable in interplanetary space near Earth—the energetic storm particle event (ESPE), and the recurrent Forbush decrease.

The processes of accretion onto the white dwarf in a cataclysmic variable are reviewed. These systems provide the most easily observable examples of accretion disks, and enable the structure of the accretion region to be studied in detail. The properties of column accretion onto magnetic cataclysmic variables are also described.

In November 1975 workers at the Herzberg Institute for Astrophysics in Canada (Avery et al. 1976) discovered cyanodiacetylene in Sgr B2. This molecule is the heaviest yet detected in interstellar space, having a molecular weight of 75 amu, and is the longest linear molecule known.

A program to determine accurate radio positions and optical identifications of southern flat-spectrum radio sources has been undertaken with the six-dish array of the Fleurs synthesis telescope at 1.4 GHz and using the SERC J sky survey. This sample covers the declination range −80° to −50° and comprises all 198 sources from the Parkes catalogue with α of > −0.5 and flux density of 0.25 Jy.

The radio astrometric phase of the program is complete. We conclude that by comparison with accurate VLBI positions the FST positions have r.m.s. uncertainties of ∼0″.9. There is no global bias in the FST positions at the 0″.2 to 0″.3 level relative to the JPL VLBI extragalactic reference frame. A comparison with positions from the Parkes catalogue shows that in the southern regions the Parkes catalogue has rms position errors of about 9″. There is no significant bias between the FST and Parkes positions.

The adjective ‘high’ when applied to the resolving power of radiotelescopes, has a meaning that has changed very rapidly during the last twenty-five years. In the late 1940s a resolving power of one degree was considered to be ‘high’.

The accepted interpretation of the low frequency turnovers in the spectra of many extragalactic radio sources is that they are due to the effects of synchrotron self-absorption, i.e. to the source becoming optically thick. It has been shown that the signs of the degrees of both linear and circular polarization for a homogeneous source at frequencies where it is optically thick are opposite to those at frequencies where it is optically thin.

The radio object associated with Sco X—1 noted by Andrew and Purton has been observed at a wavelength of 6 cm with the 210 ft radio telescope at the Australian National Radio Observatory, Parkes. At this wavelength the half-power antenna beamwidth is 4′ arc.

The Universities of Adelaide and Tasmania (UAT) have now collaborated in the preparation of four experiments on British Skylark rockets. Two independent X-ray detectors of total sensitive area 40 cm2 were flown on each of two rocket flights launched in April, 1967. The most significant result of these measurements was the discovery of Cen XR-2 and the measurement of the variation in its intensity and spectrum. The third flight, launched in December 1967, carried three X-ray detectors of total area 140 cm2. One of the main results from this flight, evidence for a new X-ray source at high galactic latitude, will be presented in the following paper.

Thirty-one radio sources have been investigated for the presence of OH-line radiation in their directions. Absorption and anomalous emission lines were observed.

The equipment and methods of observation have been described by Gardner, McGee and Robinson (1967). An aerial beamwidth of 12’.5 arc was combined with a 48-channel line receiver of bandwidths 37 and 10 kHz.