When I began my studies of solar radio astronomy, Dr J. L. Pawsey, who then led the radio astronomy group in the Division of Radiophysics, CSIRO, explained to me that the internal structure of the Sun was ‘well understood’, thanks to a lack of conflicting observational data, but that for the observable layers of the Sun, the photosphere, chromosphere and corona, a great many mysteries remained. I am sure that he would have been amused by the recent discovery that there are not enough neutrons coming from the core of the Sun. I shall devote most of my talk to matters about which we are fairly certain, but often I will only be able to give part of the story because the details have not yet emerged from the wealth of solar mysteries.

The theory of solar radio bursts remains a mystery to most astronomers and astrophysicists. The reasons for this are not hard to identify. First, the solar radioastronomical data are unfamiliar. (The observational data on solar radio bursts is being reviewed separately at this meeting (McLean 1981).) The important features of this data involve frequency-time structures in dynamic spectra, and such features are absent in data on galactic and extra galactic objects. Even for pulsars the data are obtained at discrete frequencies, and the frequency-time structures are not of major importance. Second, the theory itself involves plasma physical concepts which are unfamiliar to most physicists and astronomers. These concepts include those of plasma instabilities, microturbulence, and of particle-wave and wave-wave interactions. Third, one must also admit that there is a prejudice amongst many astronomers against solar physics: the Sun is regarded as interesting only to the extent that it can teach us about other astronomical objects. I shall return to this third point later.

In this review, I will be concentrating on problems related to the evolution of stars on the asymptotic giant branch (AGB). AGB stars are defined as stars which have completed core helium burning and have subsequently developed degenerate carbon/oxygen cores surrounded by hydrogen and helium burning shells; such stars have main sequence masses M≤9 M⊙ (Paczynski 1971; Becker and Iben 1980). In the HR diagram most AGB stars sit on the red giant branch. An exception to this rule occurs in Population II systems, where the AGB stars evolve asymptotically to the red giant branch from the blue side as the luminosity increases after completion of core helium burning on the horizontal branch.

Historically, infrared instrumentation for astronomical research has been developed by individual groups largely for their own enjoyment. The commissioning of the AAO’s infrared photometer-spectrometer (IRPS) in late 1978 provided for the first time in Australia a common-user instrument. Since then it has attracted considerable interest and is now the second most popular instrument in use at the AAT.

Infrared spectroscopy is a relatively new field in astronomy. When the study of celestial sources at wavelengths longer than 1 μm underwent a major spurt of growth in the mid-sixties, it was natural for astronomers to concentrate on broad band measurements. As detectors and instrumentation have steadily improved and the broad band characteristics of stellar sources in the IR have become better known, there has been a natural trend to higher spectral resolution. To date there has been sufficient work in IR spectroscopy to warrant several reviews on the subject. Although Australia has been late in entering this exciting and expanding field, the quality of work has more than made up for the delay. In this review I will briefly describe several projects involving IR spectra performed in Australia. Special emphasis will be placed on those experiments that cannot be done by any means other than IR spectroscopy. Also presented is a description of Australia’s next generation of spectroscopic instrumentation for the IR.

The Cross radiotelescope at the Molonglo Radio Observatory (Mills et al. 1963) came into full operation during 1967 and observations continued without interruption until 1978 when it was closed down for substantial modifications; these are now largely complete and observations have re-commenced. The decision to make some drastic changes was taken about seven years ago, although it had been evident right from the beginning that scientific returns from the Cross would drop sharply once the whole accessible sky had been surveyed. Indeed, the specifications for the original instrument were chosen to permit a subsequent conversion from 408 MHz to 1420 MHz with little extra expenditure on the reflector structure. Also, in 1972 a new form of circular polarized antenna was developed to provide a cheap mass-produced feed for 1420 MHz operation which could be easily phased and had good directional properties (Mills and Little 1972).

There is no question that Australian radio astronomers are in urgent need of a telescope which can provide high angular resolution for both line and continuum projects. Planning for the Australian Synthesis Telescope (AST) began in 1975 (see Wellington 1976; Manchester 1977), and with the guidance of the AST Steering Committee and the Design Study Committee the instrument, although it may be overshadowed in some respects by the US Very Large Array (VLA), now has enough unique features to whet the scientific appetites of all Australian astronomers. The planning has reached a critical phase — a proposal, costed at $A17.3 million (in 1980), was submitted to the Minister for Science and technology in February 1981 for funding in the August 1981 budget.

As Voyager 1 sailed through Saturn’s system of moons and rings last November 1980 it revealed new worlds not seen by man before. For centuries, since Galileo’s first telescopic observations in 1610, the satellites of Saturn had been no more than pin points of light, whilst the structure of the rings was barely resolved beyond 3 principal bands. Yet, within the space of a few hours, that picture changed dramatically as the images of these objects grew through Voyager’s cameras from mere specks into full and wondrous worlds. These pictures contained features that were not only intricate and astonishing in detail but which were, in many cases, unfamiliar and unexpected. A composite view of the Saturnian system as seen by Voyager 1 appears in Figure 1. Saturn’s rings, once thought to be broad belts of particles spread uniformly thin through billions of years of evolution and interparticle collisions, were found to be divided into hundreds of individual ringlets (Figure 2). And Cassini’s Division, a region which had been previously thought to be empty because of a ‘sweeping’ influence of Mimas, was found to contain many ringlets itself! The appearance of light and dark radial spokes in the B ring, which rotated with a velocity contrary to the law expected of Keplerian orbits, was baffling. And the F ring (Figure 3) was found to contain knots, kinks and braids which probably indicated the presence of electro-magnetic forces as well as gravitational forces (Smith et al. 1981).

One of the important discoveries of astronomy is that the Universe expands: distant galaxies have large recession velocities in direct proportion to their distances. Attempts to determine a global value for the constant of proportionality between the velocity and the distance (Hubble constant) are met with difficulties by the presence of peculiar, random and streaming motions in the local region. These peculiar motions are either of primordial origin or the effect of density perturbations. These affect the mean velocity of the nearby groups in the level of 50-100 km/sec (Tammann, Sandage and Yahil 1980). However, the expected peculiar gravitationally induced motion of the Local Group towards the Virgo cluster, could be large due to the high density contrast in that direction (Sciama 1967; de Vaucouleurs and Peters 1968; Sandage, Tammann and Hardy 1972; Jones 1976). This infall motion could be as high as 500 km/sec if the anisotropy of the microwave background is interpreted to have a component of our peculiar motion towards the Virgo cluster (Peebles 1971, Boughn, Cheng and Wilkinson 1981; Gorenstein and Smoot 1981).

The polarisation observations of the central region (containing the jet) of the galaxy M87 were obtained in May 1980, with the polarimeter (Visvanathan 1972) attached to the f/15 cassegrain focus of the AAT. The IPCS was used in direct mode to record the images of the field. Figure 1 shows a single, raw image of M87 in the light of B (the image shown is 90 arcsec square). The knots referred to in the text are marked. One complete observation consists of 12 images of the object field, corresponding to the 12 selected position angles of the polaroid filter, rotated from 0° to 330° in 30° increments. The Taurus software (Taylor and Atherton 1980) was used to increment the data to the relevant memory location. The data were stored on tape after a sufficient number of complete rotations of the polaroid were completed.

Both the radial and the velocity distributions of galaxies within rich clusters are well described by the isothermal distribution (e.g. Lewis 1978 and 1979). It is tempting to ascribe this apparently relaxed state to the operation of Lynden-BeU’s (1967) violent relaxation mechanism, during the initial coherent collapse on the proto-cluster, after it brakes itself against the universal expansion. This scenario explains the isothermal distribution observed in elliptical galaxies and globular clusters. When applied to a cluster of galaxies made up of baryons, however, the timescale for the scenario is comparable with the Hubble time H−1. The situation changes if most of the cluster mass is contributed by neutrinos.

Current results from the experiment by Reines et al (1980) on the oscillation of neutrinos from one flavour to another, if confirmed, require a non-zero rest-mass for the neutrino. Corroborative evidence can be adduced from the astrophysical consequences. In particular, the long-standing ‘missing light’ paradox in rich clusters of galaxies is solved (c.f. Cowsik and McClelland 1973), and more recent difficulties in reconciling the chronology of the Universe with both the primordial abundance of He4 and the cosmological mass density are eased (c.f. Symbalisty et al 1980). Finally Lewis (1981) shows that the concept also solves the problem of obtaining dynamically relaxed clusters of galaxies with feasable formation times. As a result, elliptical galaxies are necessarily formed from the material of a proto-cluster amid a high density of low-velocity neutrinos. This paper makes a preliminary estimate of the maximum neutrino content of elliptical galaxies.

A recent analysis of the spectra of about 2000 sources in the Culgoora-3 list (Slee 1977) of radio sources (Slee et al. 1981) has revealed some interesting features which may be the result of source evolution. The Culgoora-3 spectra were obtained by combining the 80 and 160 MHz flux densities from the Culgoora radioheliograph with other published flux data between 10 and 10,000 MHz; this is probably the most accurate set of spectra yet derived for a large number of sources selected for observation in a reasonably consistent manner. In addition to fitting the log S-log v data for each source with a straight line (its slope is the usual definition of spectral index) Slee et al. also fitted second-degree and third-degree polynomials to search for curvature in the spectra.

The radio source PKS 0511-48 is among the hundred strongest southern sources at low frequencies. It was catalogued in the Parkes survey (Ekers 1969) and mapped with the Molonglo Cross at 408 MHz by Schilizzi and McAdam (1975) with a resolution of 2′ .6 arc. It appeared in that work as a complex source, with an integrated flux density of 8.8 Jy. A search for optical identifications was made by Tritton and Schilizzi (1973), but none were found to a level of B ~ 19. We have inspected the field on the ESO B survey film, and find a group of ~ 20 faint galaxies (approximately 19-20 mag).

Our re-examination of the neutral hydrogen gas in the Small Magellan Cloud has led to four important results. Firstly, we find that Hindman’s (1967) total content HI map is a satisfactory representation of the gas in the line of sight. Secondly, we find that the HI gas in the SMC exists in four distinct large masses separated from one another in radial velocity by 20 to 30 km s−1. Thirdly, having made this division of the gas we show that there is good correlation between the radial velocities of HII regions, supergiant stars and HI. Finally, we believe that our observations reveal that the SMC is associated with an extremely large trailing halo of HI gas which forms the major component of the inter-cloud bridge region.

We present preliminary results from a programme designed to produce deep images of radio source fields drawn from the Parkes 2700 MHz and Molongolo 408 MHz catalogues using the charge-coupled-device (CCD) camera system built at the Institute of Astronomy, Cambridge. The programme is directed at a search both for faint extensions and nebulosity around radio QSOs and BL Lac objects and for faint objects in otherwise empty radio source fields; a detailed examination of the morphology of selected radio galaxies is also included.

The HR 1614 moving group of stars (Eggen 1978a) is one of a number of such groups identified by Eggen from amongst the disk population of the Galaxy (see e.g. Eggen 1969). The group was selected from a sample of 44 field stars south of + 30° declination, with right ascensions mainly > 12h and <2h, and with motions similar to that of the star HR 1614, which has a velocity of (U, V) = (−1, −58) km s−1, where U and V are the components of space motion in the direction of the galactic anticentre and galactic rotation respectively, measured relative to the Sun. The colours of these 44 stars, when plotted in a (b-y, R-I) diagram, were such that 26 of them had an excess blanketing of ~ 0.03 in b-y, measured with respect to the Hyades group. This excess blanketing was consequently chosen to be a criterion for group membership.

Carbon stars have always been amongst the most intriguing of stars which show grossly non-solar abundances. All such stars raise the questions:

(a) at what stage of stellar evolution does this peculiar abundance phase occur?

(b) do all stars pass through this stage?

(c) is the phase significant in the overall picture of galactic nucleosynthesis?

Many of the important events in the life of a star occur, or are thought to occur, during the red giant or supergiant phase of evolution. For example, in heavy and intermediate mass stars supernova explosions terminate normal evolutionary processes while in lower mass stars the stellar envelope is entirely removed giving rise to planetary nebulae and, subsequently, white dwarfs. Theoretical calculations suggest that before the onset of these rather drastic events, a significant amount of nucleosynthesis occurs, giving rise to enhanced surface abundances of He, C, N and s-process elements (e.g., Iben and Truran 1978; Renzini and Voli 1981); loss of the envelope material by stellar winds, planetary nebula ejection and supernova explosions produce overall galactic enrichment in these elements.

In astrophysics the polytropic law with index n is commonly used as a means of imposing a simple and ordered physical structure on a gaseous (or smoothed discrete) system. In many instances it would be preferable to be able to introduce a polytropic density variation analytically into the basic theory rather than numerically at the computational phase. It is perhaps unfortunate that the three well known classical analytical E type solutions of the Lane-Emden equation for n = 0, 1 and 5 all have some constraining physical features; specifically, the polytrope n = 0 has uniform density and hence arbitrary radius, when n = 1 the mass and radius are independent of each other and the solution cannot be transformed homologically, and because the first zero ξ1 = ∞ for n = 5 the corresponding polytropic model has infinite extent and central condensation. In contrast, and unlike most stars, the two finite radius models have central condensations which ~ 1.