Given an ordered set of samples {ai} of some function, then the autocorrelation of that function is the mean lagged product of these samples.

Observations of extremely high brightness temperatures in astrophysical objects imply that coherent emission processes must be occurring. An emission process may be coherent due to an inverted energy distribution leading to maser action, or due to bunching of particles in a region less than or of order of the wavelength of the radiation. Calculations of emission by bunches have generally used either a fluid model, e.g. Buschauer and Benford (1976), or a single-particle approach which requires all particles to have the same velocity, e.g. Saggion (1975) uses elements of both. In this paper we investigate gyromagnetic emission by bunches using a single-particle approach which includes the effects of differing particle velocities on the radiation.

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.

A proposal for the siting of additional 14 metre antennas for the Fleurs Synthesis Telescope (FST) was previously presented by Christiansen (1976). Since that time, difficulties have arisen which preclude the use of two of the locations. In addition, solutions to the problems of data reduction for irregular antenna spacings have been found (Frater and Skellern, 1978; Frater, 1978; Frater, 1979). It has now been possible to choose the locations of the final antennas to optimise the performance of the array within broader geographic constraints — subject now to the availability of sites on ‘friendly’ land.

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 Llanherne telescope is a meridian transit instrument with an instantaneous bandwidth of two octaves in the range 35 to 150 MHz, and was constructed primarily for studying the low frequency properties of pulsars. The antenna is a 78 × 156 metre filled aperture phased array comprising 4096 wire dipole elements arranged in a 64 × 64 matrix. Uniform illumination of the elements produces a single pencil beam response which is scanned electronically along the meridian from Declination -90° to +30°. The beamwidth at 100 MHz is 1 degree in right ascension and two degrees sec(Dec.) in declination and varies proportionally with wavelength, giving a transit time of 4 sec(Dec) × 100/f(MHz) minutes between half power points.

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 Tidbinbilla NASA Deep Space Network tracking station near Canberra employs 64-m and 34-m antennas for deep space vehicle communication. Regular use is made of the facilities for radio astronomy via a host country agreement between the United States and Australia. To support the expanding astronomical use of the station, and in particular for the Tidbinbilla two-element interferometer (Batty et al. 1977), a small computer was installed early in 1980 to control observations. The system will also be used for as much data analysis as possible to minimize off-site computing.

In the usual model of discrete cosmic X-ray sources, it is assumed that a massive star loses matter to a companion neutron star, either through a stellar wind, or by means of Roche lobe overflow into an accretion disk around the neutron star (Pines 1980). The irifalling matter becomes ionized and is channelled along the magnetic field lines of the neutron star, so that it is accreted onto the star in a very small region at the magnetic polar caps. The physical conditions at these points are assumed to be: magnetic field B ~ 1012 G, plasma temperature ~107-108 K, and infall plasma velocity ~ 0.3 c-0.5 c.

In recent years, a number of numerical experiments have simulated various aspects of the early stages of star formation (see Tscharnuter 1980 for a discussion and review). In all but one of these experiments, however, the effects of the interstellar magnetic field have been neglected, although observations (for example, see Verschuur 1969) suggest that in some interstellar clouds, the magnetic energy is comparable to, or even greater than, the gravitational and thermal energies. It is also believed (Mouschovias 1981), that at least at the early, diffuse stages of collapse, where the ionizing radiation can penetrate deep into the cloud, the bulk of the neutral matter will feel the magnetic forces via collisional coupling with the ionized matter. Thus there exist no observational, nor theoretical reasons justifying the neglect of the interstellar magnetic field in these numerical simulations.

A small astronomical observatory has been constructed on the edge of the Macquarie University campus at North Ryde in Sydney. It will be used primarily for photoelectric observations of variable stars. Further improvements to the present observing system are being planned and observations have already started on β Cepheids.

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.

The conventional method of measuring the radiation diagram of an antenna is to rotate it in the field produced by a fixed point source located in its Fraunhofer zone (Hollis et al. (1970)). With the very large antennas typically used in radio astronomy this presents difficulties. For example, to measure the 64 m telescope at ANRAO, Parkes at frequencies in the OH transition lines band (1.6-1.7 GHz), the source, to be located in the Fraunhofer zone, must be located at least 50 km away and then at a sufficiently high angle to allow measurements free from ground effects to be made. Clearly there are no terrestrial means to accomplish this.

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.

High-resolution observations indicate that very strong, small scale magnetic fields in the solar photosphere are concentrated into ropes which emerge through it. The scale of these ropes is only a few hundred kilometres across (Stenflo 1976) and their strength is estimated to vary between 1,000 and 2,000 G (Harvey 1977). These features are closely related to photospheric granular convection. The flux is observed as X-ray bright spots and sheet-like crinkles in the dark intergranular lanes, and is buffeted and shifted about by the granules (Dunn and Zirker 1973). Further, the crinkles can be resolved into separate features which outline small micropores as though a flux sheet at the end of a convection cell has separated into several isolated tubes (Galloway and Weiss 1981).

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.

Baseline ripple measurements are of two general kinds, those associated with on-source mechanisms and those with off-source mechanisms (Poulton 1974; Morris 1974). We are here principally concerned with on-source baseline ripples, which occur when a strong continuum radio source is present in the beam. The ripples are particularly conspicuous (Padman 1977, 1978) with a large instrument, such as the Parkes 64-m telescope, where the ripple period is rapid. Here baseline uncertainty becomes especially severe for the detection and study of wide lines, such as the H/He complex and the formamide multiplet near 1.54 GHz. Off-source baseline ripples also occur because of other effects, but in principle they can be removed by subtracting a reference-region spectrum taken while tracking the telescope over the same hour-angle range at the same declination under stable conditions. Improvement of the off-source baseline ripple which arises from stray radiation would also be expected to result from the technique described here.

The polytropic stellar model with index n = 0 has a uniform density distribution throughout, and consequently its physical radius is essentially arbitrary because the surface density condition, ϱ = 0, is never satisfied. This surface anomaly, which is not associated with the other polytopic models for 0 < n ≤ 5, could be a constraining factor in certain astrophysical applications involving the n = 0 polytrope. For example, in some circumstances it may be appropriate to utilize the simple physical formulation of the model but on the other hand inappropriate to disregard any zero boundary requirements for the surface density. A sequence of new E-type (as defined below) composite analytical solutions to the Lane-Emden equation, based on the indices 0 and 1, has been developed which eliminates this physical indetermination. The associated polytropic models can be classified as essentially uniform density models. Specifically, they have a large central uniform density n = 0 zone matched, in a physically consistent way, to a small outer n = 1 zone which has a steep density gradient giving ϱ = 0, along with T = 0 and P = 0, at the radial distance corresponding to the first zero of the composite solution.

Recent numerical experiments (Norman et al. 1980), which simulate the axisymmetric collapse of a rotating, self gravitating cloud, show that spurious angular momentum transport can seriously affect the evolution of the cloud. In particular, it may determine if a ring-like density enhancement will occur. The spurious angular momentum transport can arise either from an explicit artificial viscosity, which might be required if shocks occur, or from an implicit viscosity due to truncation errors in the difference equation approximation to the exact equations. In donor cell schemes like those used by Tohline (1980) and Boss (1980) spurious angular momentum transport is due to truncation errors in the difference equations. For axisymmetric problems the errors are usually not serious since the typical length of a cell in the computational grid is very much less than the length scale of the cloud. We would expect the errors to be much greater when fragmentation occurs because the length scale of a fragment may only be comparable to that of three or four cells.