The NASA Voyager spacecraft missions to the outer planets have provided a wealth of observational data with regard to the physical and chemical properties of the attendant satellite systems. Although the gaseous nebula discs from which these satellites are suspected to have formed are no longer present, these data provide at least some basis from which the characteristics of individual nebula can be deduced.

In a recent paper Aizu and Tabara list 36 radio sources classified as supernova remnants (SNR). Some of these identifications are based on low-resolution radio data and are consequently unreliable. Using the Parkes 210-foot radio telescope at 635, 1410 and 2650 MHz (beamwidth 31′, 15′ and 8′.4 respectively), E. R. Hill and the author observed the seven sources listed in Table I. Of these seven, there is close agreement with Aizu and Tabara’s data only in the last one (3C396.1), and we agree with the SNR classification, with certain reservations, for only three of these sources.

In this paper we review the evidence on the structure of the open magnetic field lines that emerge from solar active regions into interplanetary space. The evidence comes mainly from the measured sizes, positions and polarization of Type III and Type V bursts, and from electron streams observed from space. We find that the observations are best interpreted in terms of a strongly-diverging field topology, with the open field lines filling a cone of angle ~60°.

This paper is a preliminary report on the flux density monitoring of calibration sources used at the Molonglo Observatory Synthesis Telescope. We show two examples of large amplitude variability at 843 MHz which we attribute to refractive scintillation in the Galactic interstellar medium.

SN 1987A is sufficiently close to allow a unique examination of the morphology of a supernova, using speckle interferometry. Several groups [Center for Astrophysics (CfA); Imperial College (IC); Mount Stromlo and Siding Spring Observatories/Anglo-Australian Observatory (M/A)] have reported optical speckle observations. At Hα, both CfA and M/A have determined the angular extent of the emission, and reasonable agreement is obtained. The speckle-derived values are consistent with those obtained from line profiles. IC has also succeeded in resolving the supernova at Hα. At wavelengths other than Hα, at early epochs, angular diameters obtained by CfA are larger than those derived from photometric and spectroscopic measurements, possibly due to scattering effects. At later epochs, the diameters exhibit little variation between the wavelengths examined. CfA reports significant asymmetry in the late epoch data.

Several attempts have been made to re-observe (at optical wavelengths) the companion object, but none have succeeded. The nature of this phenomenon is still controversial, but the evidence indicates that the companion was real, with emission from dust apparently being the least problematic explanation. Support for this may lie in IR speckle observations (Haute Provence/Lyon) which, on about day 115, indicated the presence of one or more resolved components at an angular displacement comparable to that of the optical companion.

The classical theorems on the intensity of radiation (e.g. Milne) depend on the geometry of rectilinear ray trajectories in uniform media. In particular, the theorem concerning the specific intensity I in a medium specified by an isotropic refractive index μ—that, where there are no gains due to emission or losses due to absorption or scattering, the quantity I/μ2 = constant—is proved by assuming that the medium consists of a series of regions of constant refractive index at whose plane interfaces the coefficients of reflection are zero. For these the geometry of the trajectories (Figure 1) is such that, by Snell’s law,

With a number of important exceptions associated with transitory flare activity, most persistent sources of solar radio emission observed to date with the 80 MHz Culgoora radioheliograph have been stable in position over periods of tens of minutes or hours even though they fluctuated greatly in intensity. During several hours on 1968 November 11, however, we observed some interesting activity which showed frequent changes in the position of a source.

The classical model of the interstellar medium consists of cool clouds (typical temperature 80 K, number density 20-40 cm-3) moving through a warmer interstellar medium (104 K, 0.15-0.3 cm-3) at a rms velocity of ~ 10 km s-1. More recent models have included the coronal gas (106 K) as part of this medium. We consider the collisions of these clouds in order to determine whether these collisions initiate star formation and/or change the state of the interstellar medium.

A theory of linear acceleration emission, with possible application to pulsars, is developed. The equation of motion for a relativistic charged particle accelerated in the field of a longitudinal wave is solved to first order in the electric potential and used to derive the first order current. The power emitted and the absorption coefficient are calculated and the conditions under which masing can occur are discussed.

A survey has been made of 139 bright southern galaxies using the 1´.5 X 4° fan beam of the E-W arm of the Mills cross. These represent a largely complete sample of galaxies down to a limiting total optical magnitude of ~11.0 when corrected for Galactic absorption by 0.35 cosec β and for internal absorption due to the tilt of the emitting galaxy. Of these, 54 were detected down to a limiting radio flux of 0.4 f.u., at which level the probability of a misidentification is 10%. No a priori distinctions were made between the galaxies on the basis of strong radio emission or optical peculiarities.

In the astrophysical context, where the effects of a magnetic field on stellar convective processes have to be taken into account, we have ϰ > > η > > ν (Weiss 1977) where ϰ, η and ν are respectively the thermal, magnetic and viscous diffusivities.

On 1971 January 24 a 3B flare at 18° N., 49° W. was associated with the acceleration of protons to relativistic energies; it was one of the rare events recorded by ground-level neutron monitors. Excellent radio coverage was obtained with single-frequency radiometers in the range 1000-9400 MHz, and at Culgoora with the 8-8000 MHz spectrograph and the 80 MHz radioheliograph. At the Earth relativistic protons and electrons arrived very promptly from the flare, whose site was near the foot of the nominal interplanetary field line which connects to the Earth.

During 1971/72 the radioheliograph at Culgoora, N.S.W. was used to observe 30 bright galaxies at 80 MHz.

The Modern Laplacian Theory (Prentice 1978) of the origin of the solar system assumes a non-dissipative model of supersonic turbulence and the existence of stable rings left behind during the contraction of the proto-Sun. We show by numerical simulation that the turbulence is highly dissipative and the rings are unstable. As a result of the instability the rings spread and interact with the proto-Sun. The rings therefore cannot form in the way Prentice has proposed.

Type I storms generally occur in association with large sun-spots and the radiation is usually circularly polarized. Statistically it has been found that the sense of polarization, right-hand (RH) or left-hand (LH), usually corresponds to the ordinary magneto-ionic mode in the field of the dominant spot of the active region; when a following spot dominates, the polarization tends to be determined by this spot rather than by the leading field. One-dimensional position measurements show that the type I sources are usually not radially above the active region but are displaced by a few minutes of arc. The source sizes are about l′.2 to 4′.5 at 169 MHz and the sources frequently contain double, multiple or bipolar structure at 80 and 160 MHz.

DI Peg has been recognised as an eclipsing system since 1934 when Morgenroth (1934) discovered its variability. For over fifty years, many observers [Jensch (1934), Opalski (1936), Tsesevich (1954), Szafraniec (1956), Kruszewski (1956), Huth (1966), Rucinski (1967), Binnendijk (1973)], have studied this system. DI Peg was observed at Midway Observatory (M.O.) during 1976 and 1977 (Kennedy 1978). Considering the erratic period changes of the system, it appeared desirable to check the system again during 1980.