Over the past three years, using the Parkes Telescope, accurate positions of over 700 extragalactic radio sources have been obtained for the purpose of optical identification of the sources.

As shown recently by Y. Osaki super-massive stars with mass M < 3.5 × 105M⊙ can, in the absence of rotation, reach the hydrogen-burning main sequence before the onset of general relativistic instability. Such objects are then pulsationally unstable. A considerable simplification is introduced if one considers only very massive stars, for which the relative amplitude of the fundamental mode of oscillation is practically constant. This sets a lower limit of 104 M⊙ to the mass that can be considered. The upper limit is also reduced to 2 × 105M⊙ if one neglects the relativistic correction. One necessary step in the study of non-linear oscillations of massive stars is to derive a differential equation for the adiabatic pulsations. The relativistic correction could be taken into account in the following way.

The radio installations at Culgoora Observatory evolved from the work carried out at Dapto field station between 1952 and 1965—which in turn was based on earlier observations. The basic instrument at Dapto was a radiospectrograph which produced two solar spectra per second over a frequency range originally of 40-210 MHz and finally of 5-2000 MHz. Until 1957 the Dapto radio spectrograph was the only one operating in the world and it fell upon this instrument to reveal many of the spectral phenomena which are now well known. The spectrograph observations referred to the total flux from the Sun observations with high directivity began at Dapto in 1958 with the introduction of a swept-frequency interferometer which measured the one-dimensional (east-west) positions of bursts and their approximate angular size over a continuous range of frequencies between 40 and 70 MHz. The results obtained from this combination of spectrograph and interferometer indicated that great advances would be made in our knowledge and understanding of the phenomena if two-dimensional metre-wavelength pictures of the Sun could somehow be recorded at short time intervals of about Is—again in combination with spectrographic observations. This requirement led to the start of the radioheliograph project. One requirement for this instrument was a site with linear dimensions of the order of 3x3 km. This was far too large for the Dapto site and a new site was selected at Culgoora in the north-west plains of New South Wales. The virtues of this site are its size, flatness, freedom from flooding, low radio noise level and accessibility from Sydney by air transport. Its sunshine and optical-seeing properties also made it a highly desirable site for optical observations, and developments assumed a new significance when Dr. Giovanelli and his optical colleagues decided to join us at the same observatory.

Coronae Austrinae is one of the few star formation areas lying well away from the galactic plane (l = 360°, b = −17°) and is visible predominantly from the Southern Hemisphere.

We present here the best of a series of models of the Magellanic stream. The dominant force in these models is gas drag. Gaseous cloudlets are torn from the bridge between the Large and Small Magellanic Clouds as the Magellanic system passes through a hot gaseous halo about our galaxy. The cloudlets are then stretched apart from each other by tidal and drag forces to form the Magellanic stream. Our best model closely reproduces the position of the stream on the sky and the run of radial velocities along the Magellanic stream. The agreement is almost as good as the best purely tidal model. In our best model the Magellanic system is only loosely bound to our galaxy and is on the first encounter with it. This overcomes some of the problems with purely tidal models. Our series of models indicate that there is a wide range of parameters that will produce a reasonable stream under the forces of gas drag and gravity.

The innermost Galilean satellite of Jupiter, Io, has been observed to strongly modulate the probability and intensity of Jupiter’s decametric emissions. The effect is most pronounced at frequencies greater than 30 MHz. Radiation occurs from two configurations of Jupiter and Io, the first when Io is 90° from superior geocentric conjunction (s.g.c.) and Jupiter’s longitude is near 120°, and the second when Io is 240° from s.g.c. and Jupiter’s longitude is near 230°.

It has been suggested, for example by Wilson and Spiegel, that the results from the study of convection in incompressible fluids may provide a basis for the study of the solar convection zone. In fact Wilson’s models contain temperature fluctuation maxima, a feature exhibited by the results obtained from the convection problem for large values of the Rayleigh number.

The paraboloid primary mirror of a classical reflecting telescope gives an image that is perfectly corrected for spherical aberration and free from chromatic aberration. However, the image suffers from coma, astigmatism and field curvature. These aberrations severely limit the usable field. For example, the primary mirror of the 200 inch telescope gives an acceptable image of a field with a diameter of only ~2’ arc.

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.

A new mechanism of thermonuclear reaction is briefly introduced. It shows that a certain amount of thermonuclear reaction can take place in dense, low temperature (T < 1 × 105 K) plasmas. As most regions in the Sun are at moderate and low temperature, a sufficient amount of fusion energy is generated there. Therefore, the current standard solar models, in which the solar central temperature must be slightly lower than 15 × 106 K, must be modified, and this would make the flux of high-energy neutrinos conform with the observational results.

The exact formula for the intensity of synchrotron radiation emitted by a single charged particle in vacuo was given by Schott, for the case of circular orbits, and Takakura for the case of helical orbits. In the general case the radiated power is expressed in terms of four variables which appear in (among other places) the arguments or orders of a Bessel function and its first derivative; hence the general formula gives little insight into the interpretation of synchrotron radiation and allows evaluation only in particular cases. There is a particular need for approximate formulae that yield the spectrum of the radiation in explicit form. Such approximate formulae were found by Vladimirskii and Schwinger for the case of highly relativistic electrons. In the present paper we outline the derivation of approximate formulae applicable to mildly relativistic electrons, especially those with velocity βc such that 0 ≪ β ≲ O.9. These approximations are also relevant to the case of highly relativistic electrons in a plasma with refractive index appreciably less than unity.

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.

The statistical theory of strong three-body interactions (Monaghan 1976a, b, Nash and Monaghan 1978) is based on the assumption that the motion of the system in phase space is ergodic, and that the energy and angular momentum are the only isolating integrals. The a priori phase space is infinite because the system is not confined by walls, but this is only a formal difficulty since the numerical calculations show that the motion takes place in a finite region of ordinary space and this fact can be incorporated in the statistical description. The probability density of the system in phase space is essentially Gibb’s Micro-Canonical ensemble.

In Table I are given photometric data and spectral classes for some OB stars in galactic longitudes 298°-306°. The data have been obtained using a photoelectric photometer on the Reynolds reflector and the Meinel spectrograph on the 100 cm reflector at Siding Spring. Numbers refer to an OB star catalogue in preparation.

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.

In simulations of gas flow in the gravitational field of model barred galaxies which we have described elsewhere, structures resembling inner rings have formed. The model rings encircle the bar as observed in real galaxies, but are more elongated than the average inner ring. In this paper we show that the addition of a lens-like component to the background field results in much rounder rings. Indeed the shape and position of the model rings are very sensitive to any steep gradients in the azimuthally averaged surface density near the ends of the bar.