We review the discovery of gamma-ray bursts, and summarise the new data from the Compton Gamma-Ray Observatory. We evaluate the evidence that gamma-ray bursts are at cosmological distances, and discuss applications of such gamma-ray bursts to cosmological problems.

The initial results of a southern sky survey of the peculiar velocities of 1355 spiral galaxies by a group at Mount Stromlo and Siding Spring Observatories (MSSSO) are discussed against the background of past work in this area. The most important result is that the Great Attractor does not exist; rather, there is bulk flow relative to the cosmic microwave background (CMB) of amplitude 600 km s−1 and scale greater than 130 h−1 Mpc in the Supergalactic plane. This is generated by the assumption that the CMB dipole is Doppler induced by our Galaxy moving at 622 km s−1 relative to the CMB. This may be incorrect, in which case there is no bulk flow and the radiation dipole is cosmological in origin with important implications for the early Universe.

The theory of coronal structure and of the associated angular momentum transport by magneto-thermo-centrifugal winds is reviewed, with reference to recent observations of rapidly rotating late-type stars. In particular, the combined optical and X-ray studies of AB Doradus are consistent with the predicted picture of a hot, magnetically-controlled ‘dead zone’ in near corotation with the star, and of cooler wind-emitting regions (analogues of the solar coronal holes). The standard theory predicts a rate of angular momentum transport that depends on the extent of the wind zone, the relative importance of thermal and centrifugal driving, and the variation of the dynamo-built surface field with rotation. For stars like the Sun, with approximately one tenth of the mass in the convective envelope, detailed comparison of the theory with the observed rotations of stars in clusters of different ages is sensitive to the strength of the coupling between the envelope and the radiative core, and is constrained by helioseismological limitations on rotational shear within the present-day Sun. An inferred strong braking during the early epochs may hint at a non-standard braking model, with the Maxwell stresses dominant far from as well as near the stellar surface.

Ground-based gamma-ray astronomy has slowly developed over the past quarter of a century to a position now where a number of sources are known to produce gamma-rays in the energy range 1011eV to 1018eV. The observations are difficult, with exceptional signal to noise problems, but improved techniques are now allowing observers to proceed with confidence. In this paper the physical bases of the observations are emphasised to show the important issues in the field and the present state of the observations is indicated.

The effect of varying magnetic field strength on the frequency of oscillatory motions for cellular multimode magnetoconvection has been investigated. In addition the influence of the thermal, viscous and magnetic diffusivities have been taken into account and the range of preferred horizontal scales established. The relationship between the period of oscillation and the magnetic field strength is determined.

The results of a new imaging survey of 68 bright (mv < 18) high redshift (z > 0.7) quasars are presented. The distribution of celestial distances between the quasars and the nearest galaxy neighbours shows an excess at small separations (< 15 arcseconds) significant at the 99.96% level. The redshifts of these galaxies are not known, so two interpretations are possible. If the galaxies are in groups physically associated with the quasars then they must be significantly brighter (> 3 magnitudes) than normal M* galaxies at the present epoch. Alternatively, this may be the result of a bias caused by gravitational amplification of background quasars by compact lenses in the halos of the nearest neighbour (foreground) galaxies. Of the present sample, 25% of the quasars have extra galaxies. If this is caused by a gravitational lensing bias, then, allowing for incompleteness, the results imply that as many as 60% of bright quasars may be gravitationally lensed.

Observations of the Pluto-Charon system using the Hubble Space Telescope are soon to provide another test of the modern Laplacian theory of solar system origin. According to this theory, Pluto, Charon and Neptune’s moon Triton are condensed remnants of the gas ring which was shed by the proto-solar cloud at Neptune’s orbit, and from which Neptune formed. Each body should have the same bulk chemical composition provided that the influence of secondary events such as physical collision can be neglected. Here we report a model for the time-dependent, surface-catalysed production of CH4, solid carbon C(s) and CO2 within the outer layers of the proto-solar cloud. This model is used to determine the condensate mix which best fits the Voyager 2 spacecraft measurements of Triton’s mean density. We suggest that Triton is a chemically homogeneous structure consisting, by mass, of 44.2% anhydrous rock, 2.1% graphite, 33.0% water ice and 20.7% dry ice (i.e., solid CO2 ice, of which a fraction nearly 2/3 is present as the clathrate hydrate CO2·5.75 H2O). On the basis of this composition, the individual mean densities of Pluto and Charon are predicted to be 2.02 ± 0.02 g/cm3 and 1.94 ± 0.02 g/cm3, respectively, assuming a mean surface temperature of 35 K. The mean density of the combined system is predicted to be 2.01 ± 0.02 g/cm3.

Described here is the new infrared camera/spectrograph, IRIS, that was brought into operation at the Anglo-Australian Telescope early in 1991. A number of scientific discoveries are used to demonstrate the capabilities of the instrument.

Ring-width time series obtained from Engelmann Spruce trees growing at high altitude sites in the Rocky Mountains, Colorado, exhibit dominant 11-year spectral periodicities. A significant linear cross-correlation also exists between these series and the Zurich series of annual sunspot numbers. A regression model based on these proxy data has been developed for the annual variation of the 11-year solar cycle. It is established that over the calibration period a very high percentage of the variance (40%) in growth patterns, contributed by a single source, can be explained by solar variation. The model correlates with the Zürich series of sunspot numbers at the 99% significance level post 1870 AD. However, over the total period 1700–1870 AD the comparison was found to be not statistically significant at lag 0. Some possible reasons for this are considered.

In this article I review our understanding of s-process nucleosynthesis in Asymptotic Giant Branch (AGB) stars. The discussion begins with the nuclear back~ ground and then shows how the required conditions are found in thermally pulsing AGB stars. The two competing neutron sources (Ne22 and C13) are discussed, as is the observational and theoretical evidence for and against each of them. We conclude by discussing the recent evidence for hot bottom burning, including the observed enhancements of Li7 and Al26 in some AGB stars.

The loss-cone-driven electron cyclotron maser instability is widely believed to be responsible for millisecond bursts of intense microwave emission often observed during solar flares. However, the maser radiation is strongly absorbed as it propagates outward from the corona and existing analytical models predict that this absorption should be sufficiently strong to prevent observable levels of the radiation from escaping, except under highly restrictive conditions. In order to address the problem of how microwave spike bursts can be observed at all, we present a numerical ray-tracing analysis which incorporates emission, propagation and absorption of fundamental cyclotron maser radiation in a realistic model of a coronal flux loop. It is found that the radiation can escape to a potential observer and that the physical conditions under which escape occurs are more restrictive for fundamental emission in the extraordinary (x)-mode than in the ordinary (0)-mode. Escaping radiation in the x-mode is found to be highly directional and chiefly observable toward the center of the solar disk, while escaping 0-mode radiation is found to emerge from the corona over a much wider range of directions, with some cases corresponding to observable radiation near the solar limb.

Among the most important stimuli for developing the FLAIR multi-object spectroscopy system on the 1.2-m UK Schmidt Telescope was its potential for carrying out large-scale redshift surveys of galaxies of intermediate magnitude (B <~ 17). During FLAIR’s lengthy development period, these objects provided the yardstick by which the system’s performance was measured, and a number of limited-area redshift surveys were carried out. We are now following these with a 1-in-3 survey over the 60 fields of the ROE/Durham Galaxy Catalogue to produce a redshift map of some 4000 galaxies out to a distance of ~ 300h−1 Mpc (where the parameter h is the Hubble constant expressed as a fraction of 100 kms−1 Mpc−1). In this paper we summarise the results from our redshift surveys to highlight the capabilities of FLAIR. We present a status report on the current large-scale survey, and show that the recently-introduced FLAIR II system will speed its progress considerably.

Clumpy, intense wave packets observed in situ in the Jovian and terrestrial electron foreshocks, and in the Earth’s auroral acceleration zone, point to the existence of non-linear plasma turbulence in these regions. In non-linear turbulence, wave packets collapse to short scales and high fields, stopping only when coherent wave-particle interactions efficiently dissipate the energy in the waves. The purpose of this paper is to examine the shortest scales and highest fields achieved during collapse in a strongly magnetised plasma, and identify parts of the solar system where the magnetised aspects of wave collapse are important.

We present near-infrared images and spectra of the peculiar radio galaxy Centaurus A. The images reveal extended emission regions at the longer wavelengths and show colours characteristic of reddened starlight. We believe we are seeing stars within the warped disc of Cen A, which are obscured in the optical by dust. Both images and spectra indicate the presence of a compact core, whose colours are much redder than those of the surrounding stars. In the spectrum of the core, detections have been made of [Fe II] 1.644 μm, H2 2.122 μm and Br γ. These lines appear to peak on the nucleus and their presence and width suggest starburst activity.

We present 6 cm Australia Telescope images of 22 strong southern radio sources. At least one of these sources appears likely to be a gravitationally lensed mirage.

The availability of Magellan radar images of Venus on CDROM allows small research groups to engage in planetary physics projects using simple image processing systems. The material lends itself to short projects for high school students or Masters students.

Our initial investigations using the Magellan data have evolved into a Masters project which concentrates on the morphology of small scale structures which have terrestrial counterparts. These include studies of volcanic cone fields, lava tubes and other collapse features, and impact features.

Our current understanding of Herbig-Haro objects and their relationship with outflows and Pre-Main-Sequence objects is limited. Although the general mechanism of outflows is understood, the detailed questions concerning the outflowing material’s origin and the collimation mechanisms remain largely unanswered. The role of multi-waveband observations (visible, infrared and radio) is vital to our understanding of the shock dynamics of outflows.

This paper discusses high spatial resolution near infrared maps of three outflow complexes, HH34, HH46/HH47 and HH54, made using the Anglo Australian Observatory’s infrared camera, IRIS. For the first time molecular hydrogen emission is observed associated with the edges of outflow cavities. In the cases of HH46/47 and to a lesser extent HH34 molecular emission is seen coincident with highly collimated jets feeding the outflow cavities.

Active Galactic Nuclei (AGN) occur with widely differing characteristics of luminosity, variability and non-thermal emission. Although it is generally accepted that all such objects are powered by the accretion of matter to a super-massive black hole, no convincing model has been proposed which accounts for the diversity of observed phenomena. The model described here is based upon the hypothesis that shear flows in a misaligned accretion disc around a Kerr black hole lead to the growth of dynamical instabilities which disrupt the disc near the Bardeen-Petterson radius. Resulting clouds of disc material are fragmented by collisions and ablated by radiation from the compact core to produce a hot Parker wind which is optically thick to electron scattering. Within this wind, many fragments of disc material are entrained and photoionised to produce the broad emission lines, while some are accreted to power the system. Usually the wind impedes jet flows, in which case the object is radio quiet. When the disc and black hole are only slightly misaligned, however, the wind is equatorially biased and collimated axial jets may form. Such objects will be radio loud, and may exhibit superluminal phenomena if the jet is oriented close to the line of sight.

strong non-thermal radio sources at low galactic latitude may be young galactic supernova remnants or else distant extragalactic objects located in the direction of the galactic plane merely by chance. Here, we have imaged G321.48 + 1.02 with the Australia Telescope in order to distinguish between these alternatives for this source.

The CANGAROO project incorporates two Čerenkov imaging telescopes at Woomera to obtain stereo images of very high-energy gamma-ray (and cosmic-ray) showers. The first stereo observations, with one imaging system, were made in March 1992, and preliminary stereo imaging observations began in July 1992. This paper describes the stereo imaging technique, the sources under investigation, and the indications from the first data sets.