Theoretical work on the radio emission from supernova remnants (SNRs) has not developed much since the pioneering work of Shklovsky (1960) and van der Laa (1962a, b). Despite agreement that the emission results from the synchrotron process, the origin of the relativistic particles and magnetic field is not clear. There are three reasonable alternatives:

1. (i) particles and field originate within the ejected material (e.g. Shklovsky 1960);

2. (ii) both field and particles originate in the compressed interstellar medium (e.g. van der Laan 1962a);

3. (iii) the field is interstellar but the particles are from the ejecta (as outlined by van der Laan 1962b).

The radio emission from Jupiter in the frequency range from ∽ 50 MHz to ∽ 5 GHz is mainly synchrotron emission from electrons in the intense radiation belt which surrounds Jupiter out to several planetary radii. Information about the pitch angles of these electrons can be derived both from the radio observations and from the Pioneer space probe observations. In this communication we discuss the pitch angle distribution inferred from the radio data and the apparent conflict with the Pioneer data.

Cas A has a radio surface brightness much higher (by a factor of about 100) than that of any other galactic supernova remnant (SNR) and is probably the youngest (≤ 300 yr). It therefore provides unique information on young remnants, but this very uniqueness makes it hazardous to treat Cas A as a typical remnant. However, because it (i) shows a clearly defined shell of radio emission of much the same type as older remnants, and (ii) lies approximately on the extrapolation of the Σ.-D (surface brightness-diameter) relationship derived for older remnants (Clark and Caswell 1976); Caswell and Lerche 1979a), detailed comparison with older remnants seems appropriate.

The MC2 and MC3 catalogues cover two strips approximately 2° wide centred on declinations +11° and +16.5°. MC2 runs from 11h 28m to 01h 23m and MC3 from 13h 31m to 04h 11m (Sutton et al. 1974). Optical identifications up to 17h 00m have been’published (Hazard and Murdoch 1977) and identifications for the remainder exist in preliminary form (Hazard, Zotov and Murdoch, in preparation). Optical spectra are being obtained chiefly at Lick Observatory (Smith et al. 1977) and this programme is now approaching completion.

The University of Tasmania balloon-borne large area X-ray telescope was flown from Alice Springs on 20 November 1978. A number of known X-ray sources were observed and a transient increase believed to be a gamma ray burst was detected.

Since the discovery of highly masering OH emission, and later of H2O masers, there has been little progress made in understanding their geometry and structure. Although both OH and H2O spectra are highly complex, no one has been able to ‘decode’ the information from the many individual features. Knowles and Batchelor (1976) have recently suggested that many water vapour spectra have a symmetrical character, with one or more pairs of features equally spaced in radial velocity about a central axis. It is here proposed that a similar symmetry exists in HH-region OH masers as well as main-line OH stars such as VY CMa. We also demonstrate that features at close to the same radial velocity are often present in several different OH and H2O transitions and probably come from the same masering cloud. From this widely applicable empirical observational model we then make a few simple deductions about the possible geometry of such masering regions.

Most supernova remnants (SNRs) show a ring-shaped radio intensity distribution which is interpreted as the projection of an approximately spherical shell of emission. However, in many cases the ring is neither circular nor complete; in this empirical investigation a major factor responsible for asymmetry is identified and the implications of this discovery are explored.

One of the critical parameters for a theory of emission from QSOs is the time scale of the variations in this emission. For many sources, changes occur faster than the light travel time across the source disk size as determined by VLBI observations. If the decimetre flux density is assumed to come from a small core, appropriate to the time scale of its variations then the brightness temperature must be far greater than ~ 1012 K allowed by the incoherent synchrotron process. These difficulties have been examined (Jones and Burbidge 1973; Burbidge and Stein 1975) using the QSO 2251 + 158 (3C454.3) as an example against which to test the theory. In this paper, I examine the time scale of the variations in 46 sources and show that most of these vary significantly within 2 years. The most rapid changes are in the QSOs 0736 + 017 and 1504–166 which have changed 40% within a few months — an order of magnitude faster than 2251 + 158.

In this paper we report an independent determination of the Location of the break (change in spectral index) in the spectrum of the diffuse X-ray background by applying a simple analysis technique to data already in the literature.

About 1 km to the east of the township of Windsor, NSW and only 50 ft above mean tide level, stands the remains of one of the first observatories in Australia. Here John Tebbutt established his private observatory and for over 60 years continued a remarkable career as a gentleman astronomer in the best tradition of 19th century Europe.

It has been accepted since the mid-1950’s that the LMC is a flat rotating body, with its plane inclined at an angle of about 27° to the line of sight and so nearly face on, and its line of nodes running 10° west of north (de Vaucouleurs and Freeman 1972). The inclination is inferred from the ellipticity of the outermost optical and radio isophotes but there has been no convincing way to fix its sense — whether the E or W side is nearer. Some years ago the late Dr David Thackeray suggested to one of us (SCBG) that this could be done by comparing the magnitudes of cepheids on the extreme E and W sides of the Cloud. With the discovery of the Magellanic Stream and the great increase of interest in the spatial geometry and dynamics of the Clouds and Galaxy complex, the sense of the tilt of the LMC has become a matter of importance, and we decided to go ahead with the project.

The problem of radiative transfer in the presence of a magnetic field may be formulated in terms of four interdependent differential equations for the four Stokes parameters I, Q, U and V (Hardorp et al. 1976)

Most of the known 1.35 cm water vapour masers have been detected in the direction of known 18 cm OH masers. However, a small number have been found in the direction of HII regions where no OH maser is known. Several new examples of H20 masers with no known OH counterparts have recently been published by Kaufmann et d. (1976), who suggest that these constitute a new class of H20 maser.

The primary function of the 64-m telescope, situated at Tidbinbilla near Canberra, is to communicate with and to control NASA’s unmanned interplanetary space craft (Reid et al. 1973). Similar telescopes are situated at Goldstone in California and in Madrid and are part of the NASA-JPL Deep Space Network (DSN). Under the Host Country Radio Science Agreement between the U.S. and Australia the telescope is available to Australian astronomers at times outside those committed to normal tracking. A radiometer operating at λ = 13.5 mm has been built by CSIRO for use on the 64-m telescope. It was initially used for VLBI observations of water vapour masers on baselines between the U.S., Australia and USSR (Batchelor et al. 1976).