It has long been known that Fraunhofer lines show variations in intensity from place to place over the Sun’s surface, these being particularly noticeable in spectroheliograms obtained in the strong chromospheric lines. An early account of the weaker Unes was given by d’Azam-buja. McMath, Mohler, Pierce and Goldberg attributed intensity increases in (or decreases in depth of) metallic spectral lines to local temperature increases. Sheeley used high-resolution spectra to study these line weakenings further, finding them where, and only where, strong non-spot magnetic fields occurred. He also reported that in many cases the continuum in such regions was of reduced intensity, suggesting that fields often occur in the dark lanes and pores in the granulation. Spectroheliograms obtained in the cores of the weakened lines (e.g., Fel 6302.5Å) by Chapman and Sheeley showed that the bright network which these weakenings form appears as a sequence of sharp, bright points in the cores of the fainter lines and the wings of stronger lines but is more diffuse in the cores of stronger lines. They found the bright network in Zeeman-insensitive Unes (e.g., 5123.7A) also, indicating that it is due, at least in part, to variations in physical conditions. Lines of low ionization and excitation are weakened more than those of high ionization and excitation, and they attributed this to a temperature increase by 100-200 °K in the region of formation of the line cores ; a similar increase of 250 °K was found by Harvey and Livingston.

A knowledge of the quantitative chemical composition of the primordial solar system must underlie all comprehensive studies of its origin and evolution. Usually we take the composition of the surface layers (photosphere) of the Sun as representative of this composition (except perhaps for deuterium, Li, B, and Be).

In conjunction with the Stellar Interferometer project at Sydney University, a shearing interferometer system has been constructed to measure the atmospheric ‘seeing’ in real time using a portable telescope. The interferometric method allows direct measurement of the parameter r o, which derives from the theory of atmospheric turbulence. This permits reliable comparison with ‘seeing’ determinations by other methods. This paper briefly describes the instrument and presents initial results of the observing program.

We present spectropolarimetric observations of the eclipsing cataclysmic variable 1H1752+08. Modelling of the line intensity and polarisation spectra of 1H1752+08 shows that the magnetic field structure of the white dwarf is off-centre and the mean photospheric field strength is about 7 MG, the lowest measured in a cataclysmic variable (CV). We argue that 1H1752+08 is most probably a low-field AM Herculis system.

The evolution of asymptotic giant branch (AGB) stars as a function of mass and composition has been studied by Becker and Iben (1979, 1980) for M≥3 M⊙. The results from calculations like these may be used to provide input data for calculations of synthetic AGB star populations, as has been done by Wood and Cahn (1977), Iben (1981) and Renzini and Voli (1981).

In this paper we present the results of spectroscopic observations for 34 emission-line stars (ELSs) in the Orion belt region, which were detected in an extensive survery. Spectral classification and the intensities of Hα and Hβ emission have revealed that the observed ELSs are probably T-Tauri type stars.

From an assessment of recent high-resolution galactic radio surveys, in the continuum and in the H109oc recombination line, the author has detected or confirmed over 90 non-thermal sources, most likely all supernova remnants.1 The distances to each of these objects have also been estimated, from an empirical surface-brightness linear-size relationship derived from 15 remnants whose distances are known from either a comparison of the radial velocities and proper motions of filaments in the nebula, neutral hydrogen absorption measurements, or association of the remnant with an object of known distance. In this note we wish to remark on the galactic distribution of supernova remnants and the possible association of these objects with pulsars and X-ray sources.

For the past six years astronomers have been regarding the universe through a new window—the X-ray window. In these six years this subject has experienced a ‘remarkable’ growth. In late 1966 workers from the Naval Research Laboratory (NRL) published a catalogue containing 35 X-ray sources. In my preparation for this report I have compiled a new catalogue containing only 22 sources (which I believe contains all of the presently confirmed X-ray sources). This early proliferation of ‘sources’ may be attributed to the exuberance of the experimenters or perhaps to a poor understanding of the laws of statistics. A simple calculation shows that, with this rate of decrease of ‘observable’ sources, X-ray astronomy will cease to exist as a subject in 1972!

Studies of solar absorption line profiles obtained at high spatial and spectral resolution have usually been content to extract one parameter (the frequency shift in the core of the line) from each profile to describe the velocity field. However, attempts have been made to obtain the variation of velocity with depth in the solar atmosphere either by simultaneous observation of the frequency shift in the cores of several lines with different excitation potentials or by measuring the bisector-shift in a single line profile as described by Kulander and Jefferies (1966). In the first method it is necessary to assign a depth of formation to the core of each line used while in the second method a depth of formation has to be assigned to each point in the line profile. Parnell and Beckers (1969) have discussed the problems involved in assigning a depth on formation and in particular they have shown that when a velocity field is present the concept of depth of formation is dependent of the velocity field. In this contribution we describe a method of determining the velocity field from a single line profile which does not suffer from the problems associated with methods based on the concept of depth of formation.

It has long been suspected that winds of thermal and/or relativistic particles are a common feature of both active and normal galaxies. Galactic winds are likely to be an important mechanism, particularly at high redshift, by which energy and metals from galaxies are subsequently dumped into the intergalactic medium. Both observational and theoretical studies of wind processes remain in their infancy, largely because astrophysical winds are difficult to detect. Future satellite missions will make systematic surveys possible for the first time. In this review, we summarise the current evidence for galactic-scale winds, particularly in energy bands where the wind emission is spatially resolved. We also discuss observational limitations and problems of interpretation.

Astronomy is one of the most ancient disciplines of knowledge which has inspired a great deal of human thought. Its study has triggered developments in many fields. Bohr’s atomic model and our idea about the thermonuclear fusion are two of the many examples which have significantly influenced (and will continue to influence) the course of human civilisation.

In a previous paper it was shown how one could improve upon the Böhm-Vitense model of the solar convection zone by the inclusion of four different length scales and by the determination of these length scales with the use of the quasi-Vitense model as developed by Unno. In this way the vertical wave number kz , associated with a characteristic eddy, can be determined by the integration of a second order differential equation. The integrations have to be started at a suitable depth and all model calculations depend critically on the assumed structure of the top layer.

When a rotating magnetised system (angular speed Ω), such as a planet or star, loses mass there is necessarily an energy dissipation associated with the mass loss. Consider mass loss at rate M, such that the matter is flung off with the orbital speed ΩR 1, at a radius R 1 ≫ R 0, where R 0 is the radius of the planet or star. The power released is approximately equal to the power P rot = 1/2MΩ2 R 2 carried off in rotational kinetic energy. Part of the energy released is carried off as magnetic energy in the escaping plasma, and the remainder is released through dissipation of currents. Such dissipation plausibly leads to the acceleration of particles. The power released should be important for Jupiter and for some rapidly rotating stars. For most stellar systems, the power released is small compared to that required to drive a wind.

In recent years, cosmic-rays have become part of the study of astrophysics and the search for information as to their origin has assumed considerable importance. The question of the origin of the rays is linked with questions concerning their acceleration and propagation through interstellar space. The main problem facing the cosmic-ray astrophysicist in attempting to elucidate these questions observationally arises from the fact that most particles are electrically charged, causing their paths to be curved by the magnetic fields of the Earth and interplanetary and interstellar space.

Elliptical galaxies are at first sight a remarkably homogenous class of objects, yet some of them produce large and enormously powerful radio sources while others remain more or less quiescent. Why should this be so? What prompts the nucleus of an elliptical galaxy to become ‘active’? What, if anything, do elliptical galaxies have in common with the bulges of spirals? Here, I review some of the radio and optical properties of nearby elliptical galaxies, with special emphasis on events which take place within the central kiloparsec.

It is likely that in most stars certain layers, either in the interior or outer regions, will be unstable against convection and the study of energy transport by convection has raised considerable interest since the early days of this century when Karl Schwarzschild derived his criterion for deciding whether a certain region is in convective or radiative equilibrium.

Microwave line investigations have shown that several bright southern galaxies contain dense molecular clouds overlying bright radio nuclei (see e.g. Whiteoak 1978). In terms of general kinematic models of galaxies the clouds have velocities that are anomalous, being consistent with radial motions both towards and away from the nucleus. To extend our knowledge of these motions we are investigating the distribution of optical spectral lines near the nuclei of the galaxies. We present here preliminary results for NGC 4945 and 5128.