The most obvious feature of the polarization of the radio emission from most pulsars is the rotation of the plane of linear polarization across pulses. The original interpretation of this in terms of the magnetic pole model (Radhakrishnan 1969, Radhakrishnan et al. 1969, Radhakrishnan and Cooke 1969) accounts for the variation of position angle extremely well for some pulsars (e.g. Manchester and Taylor 1977, Manchester 1978). Conversely, this provides strong support for the magnetic pole model for pulsar emission. It also suggests that the emission is basically linearly polarized as implied by virtually all proposed emission mechanisms, e.g. the reviews by Ginzburg and Zheleznyakov (1975) and Arons (1979). However, there are two features of the polarization which require a separate explanation. First, some pulsars have a moderately high degree of circular polarization, even in the integrated pulse profile (Manchester 1971, Lyne, Smith and Graham 1971). In some pulsars the average degree of circular polarization can exceed the average degree of linear polarization, e.g. in PSR 0835-41 and 0959-54 (McCulloch et al. 1978). Second, some pulsars exhibit the phenomenon of transitions between orthogonal elliptical polarizations (Manchester, Taylor and Huguenin 1975, Backer, Rankin and Campbell 1976, Cordes and Hankins 1977, Cordes, Rankin and Backer 1978). In many pulsars the orthogonal polarizations have substantial circular components, e.g. in PSR 1133 + 16 (Manchester et al. 1975) and PSR 2020 + 28 (Cordes et al. 1978).

The reliable detection and identification of weak, small-diameter radio sources require an instrument with both high sensitivity and high positional accuracy.

In solar physics a need exists for filters which have very narrow passbands, ~0.01 nm or less. While Lyot-Öhman birefringent filters have been used particularly for investigations at the Hα line, the limited availability of the raw materials, especially calcite, have usually restricted these filters to passbands of ~ 0.025 nm or more. A possible alternative type of filter consists of a number of Fabry-Perot interferometers mounted one behind the other.

During the past year we have investigated 72 regions in the galactic plane at 408 and 5000 MHz using the Molonglo and Parkes radio telescopes, respectively.

Although the synchrotron emission from a single electron moving with an ultrarelativistic velocity βc in a magnetic field B 0 is elliptically polarized, the characteristics of the polarization ellipse being determined by the position of the direction of observation n relative to the cone swept out by the direction u of the velocity vector about the direction of B 0, the resultant emission from a distribution of such gyrating electrons is, to a first approximation, linearly polarized in the direction perpendicular to the projection of B 0 on to the plane transverse to n. The reasons for this are that for a single electron the emission is effectively confined to within a small angular distance O(ξ) of u, where ξ = √ (1 −β 2) ≪ 1 and that (i) the fourth Stokes parameter is to this approximation an odd function of the angle ip between n and u at its closest approach, and (ii) the number of electrons passing within equal angular distances ψ = ±O(ξ) are equal. It follows that if ξ is large enough it is possible for the next approximation to the fourth Stokes parameter for a distribution of electrons to be significant, so that the resultant emission is elliptically polarized.

The anomalously high density of the planet Mercury and the higher-than-solar rock-to-ice ratio in Jupiter’s moons Ganymede and Callisto cannot be explained by the conventional disc models of solar system formation. It is shown here that the unusual chemical signature of these bodies is the outcome of a process of chemical fractionation and orbital focussing which is peculiar to gas ring models of planet and regular satellite formation. Good numerical agreement with the observational data is obtained if the temperature of condensation of the planetary system closely followed the law T n ≃ 680[R ⊕/R n]0.9 K, where R n denotes the radial distance from the Sun.

The polarization properties of cylindrical magnetic accretion columns are calculated allowing for electron scattering within the emission region. The results are used to estimate the effects of electron scattering and geometry on the observed properties of AM Herculis type systems.

A large number of barred spiral galaxies contain a ring-like structure surrounding the bar. This is known as an inner ring if the bar terminates at the ring. Structures which are not closed but which appear to be related phenomena are given the name pseudo-inner rings by de Vaucouleurs (1959).

The geographic South Pole, where the United States maintains a year-round scientific station, affords a number of unique advantages for certain types of astronomical observations. These include: continuous viewing and constant declination of ail objects in the southern celestial hemisphere, exceedingly low humidity, extended periods of coronal seeing, high altitude, and uniform terrain. The areas of research that have already benefited immensely from thèse extraordinary features are helioseismology and submillimeter astronomy. Unparalleled observations of global solar oscillations have already yielded significant information about the structure and dynamics of the Sun’s interior. Far infrared measurements of various galactic and extra-galactic regions have attained an unprecedented level of sensitivity, limited for the first time only by the noise inherent in the detector. In addition to further helioseismological observations, currently planned future activities include observational cosmology and ultra high energy gamma ray astronomy.

A survey of the optical spectra of IRAS galaxies, made with the AAT, has shown that the majority have strong emission lines. Ratios of the emission lines have been plotted on the Veilleux-Osterbrock diagram ([O III]/Hβ against [N II]/Hα); this shows that the IRAS galaxies comprise several classes. In our sample the majority appear to be starburst galaxies, but Seyfert, Liner and narrow-line galaxies are also represented. Co-added spectra of the galaxy classes are presented. On the basis of optical spectroscopy, it appears that the starburst phenomenon is capable of generating luminosities exceeding 1012L ⊙.

The eighth magnitude star HD 101065 has an extremely peculiar spectrum dominated by very numerous lines of the rare earths (with only the one possible exception of ytterbium, whose lines are difficult to identify). Besides the rare earths only strontium, yttrium and zirconium could be found in substantial quantities, while calcium though present is highly underabundant. The most surprising feature of the star is the absence of iron peak elements in its spectrum.

We present here the low-dispersion optical spectra of 295 QSO candidates. The great majority of the objects were originally selected as QSOs from the Parkes 2700 MHz radio survey, although we have also included spectra of several optically selected QSOs. A few of the QSO candidates are now better described as radio galaxies and BL Lac objects. This collection of spectra is not suitable for statistical studies unless due consideration is given to selection effects.

X-ray data show that substantial quantities of hot gas are cooling near the centres of many clusters and groups of galaxies. The existence of such cooling flows has been challenged because of the lack of evidence for star formation from the cooled gas. Spectra of cooling flow galaxies show filling in of the continuum shortward of the break at 4000 Å relative to normal elliptical galaxies. This is consistent with some continuing star formation. Extended regions of line emission are commonly associated with cooling flows. If the initial-mass-function of the newly formed stars which affect the 4000 Å break is like that which applies in the solar neighbourhood, then these stars can also power the line emission. The strength of the 4000 Å break is shown to correlate with the Hβ flux in the manner expected when this is the case. This allows us to esimate the star formation rate from the line luminosity.

The rate of star formation required to account for the line emission still falls well short of the rate at which gas is inferred to be cooling. It is argued that, nevertheless, the cooling gas is probably forming into stars. The overall initial-mass-function must be different from that which applies in the solar neighbourhood, but this should not be surprising given the different ambient conditions in a cooling flow.

Since 1971, the Llanherne low frequency radio telescope (Ellis 1972) has been used to conduct surveys of the sky at several decametric wavelengths. Prior to 1974, only pen recordings on paper chart for one declination at each of the wavelengths were obtained each night and all the work to produce the final sky maps was to have been done by hand. However in 1974, a general purpose digital minicomputer (a Digital Equipment Corporation PDP 8/E) has considerably increased the research capabilities of the telescope. In the continuum sky surveys profiles at several different declinations are now obtained each night. In addition all the information gathered in an observing session is written onto magnetic tape which is later analysed on the University of Tasmania’s computer (an Elliot-503) thus providing the possibility of removing much of the tedious manual work in preparing the final sky maps. This paper describes the system developed by the author which is used by Cane (1975) to obtain the profiles from which the sky maps are being compiled.

The extensive body of broad-band photometric data for SN 1987A obtained at SAAO has been used to derive the bolometric light curve up to day 450 after the outburst. The salient features of the curve are discussed in this paper.

A moving type IV radio source on 1970 March 21 was observed with the 80 MHz Culgoora radioheliograph to move out to a distance of p = 6 (where p = R/R®). Starting as a single source of complex shape it later developed strong circular polarization (> 90% R.H.) and separated into components which retained the same polarization. The source appeared soon after a prominence eruption (or flare spray) from which some of the ejected matter travelled in the same direction as, and with a velocity close to, that of the radio source.

Astronomy and astrophysics subjects at the University of Wollongong are seen as a vehicle for emphasising and clarifying concepts in the physics degree course. They also serve to introduce both undergraduate and postgraduate students to skills in computing and instrumentation not encountered in traditional subjects.

The extended radio source 0319-453 (MSH 03-43) was observed with the Molonglo Observatory Synthesis Telescope as part of a program to study a large sample of southern extragalactic radio sources. The low level structure showed a ridge pointing towards the nearby source 0317-456, which also showed low level structure. It is suggested that the two sources are the asymmetric lobes of a radio galaxy identified with the magnitude 15 peculiar dust-land galaxy AM 0319-452. The galaxy redshift of z = 0.0633 and the radio size of 25.6 arcmin give a projected size of 1.27 Mpc (H = 100 kms−1 Mpc−1). Thus it is one of the largest radio galaxies.

The Ca II K line serves as an important tool in determining the physics of the photosphere-chromosphere region of the solar atmosphere (Cram 1983). To date detailed analyses have centred on the study of line intensity profiles.