Recent reviews have demonstrated that a wide ranging selection of objects emit a major proportion of their energy at wavelengths longer than 1 µm, including such intrinsically different objects as late type stars, Be stars, F supergiants and novae. In the majority of cases the infrared radiation has been interpreted in terms of thermal radiation from a circumstellar shell of solid ‘dust’ particles. Any attempt at a detailed comparison of theoretical energy distributions with observed infrared photometry encounters the problems of uncertainties in the absolute calibration, and limited accuracy of the observations.

Both Holmberg (1961) and de Vaucouleurs (1963, 1973) found a significant difference between the mean velocities of the different morphological types in the Virgo cluster of galaxies. To check on any dependence of this result upon spatial distribution, Lewis (1975) plotted the position of every object in the compilation of de Vaucouleurs (1961) as a function of its type. Figure 1 is the resulting plot for the elliptical galaxies, which appear to lie within two well-defined and well-separated groups. The principal parameters of these groups are listed in Table I. Arp (1967) briefly noted the linear form of the northern group centred on NGC 4486. This paper examines the evidence for the physical existence of these groups.

A Hα flare (12°N., 49°W.) on 1968 August 23d23h45m was followed by a short-lived type II burst whose dynamic spectrum, as recorded with the Culgoora radio-spectrograph, is shown in Figure 1. The type II burst had split-band structure; the upper band drifted from 130 MHz to 80 MHz, the lower band from 100 MHz to below 80 MHz (at the time the 25-74 MHz band of the spectrograph was less sensitive than the 74-220 MHz). Unusual spectral features can be seen in each split band. The most remarkable one is an absorption feature between 23h52m02s and 23h52m 10s – the depression in the bright type II emission along an ‘inverted U’ (between 120 and 85 MHz). Several other similar, though less marked, absorption features can be found between 23h51m45s and 23h52m30s.

The high radio positional accuracy now being achieved with long baseline interferometers, aperture-synthesis instruments and large filled-aperture telescopes makes the rapid and reliable processing of optical identifications essential. For some time now the customary approach for large surveys has been to carry out a search for possible radio-optical associations using the prints of the Palomar Sky Survey. Rough positions for optical counterparts have generally been estimated by interpolation within a small grid centred on the radio position. However, the final confirmation or rejection of the identifications has awaited spectroscopic or accurate positional data from one of the large optical telescopes, usually the 48-inch Schmidt or 200-inch reflector at Mt Palomar. It is becoming increasingly evident that not only is this process rather slow but it also means that preliminary interpretive work dealing with the identification content of a radio survey will be necessarily limited in scope.

T Centauri (HD119090) is a semi-regular variable with a period of 90d.61. The period is apparently stable but the photometry does not repeat very closely from cycle to cycle. The general Catalogue of Variable Stars gives a range of magnitudes from 5.5 to 9.0 and spectral types from KOe to M4IIe.

The Mount Stromio optical pulsar detection equipment is built around a commercial two-track tape recorder: one track records timing pulses, and the other the pulses from a photomultiplier (Peterson 1974). Because of the modest frequency range of the recorder, it has been necessary to introduce a scaler between the recorder and photomultiplier in order to cope with bright sources.

Centaurus X-3 was first observed by Chodil et al. in the energy range 2-9.5 Kev in 1967. Subsequent observations by Cooke and Pounds in the energy range 1-12 Kev snowed that the source was variable. Periodic X-ray pulses from Centaurus X-3 in the energy range 1-20 Kev have been discovered by Giacconi et al. They found that 70% of the X-ray energy was emitted in a pulse during 30% of a cycle. The length of the cycle is about 4.84 sec, but it was found to change by ~0.1% in a few days and by ~1% in three months. The X-ray data locate the source at 11h21.8m -60°25.8′ (1950) with an error of ±5′ arc.

The most prominent features in the spectra of Sgr A and Sgr B2 between 1636 and 1640 MHz are absorption lines corresponding to the 2π3/2, J = 3/2 ground state transitions of the isotropic species 18OH, which have rest frequencies of 1637.5 and 1639.4 MHz (Rogers and Barrett 1966). As a result of Doppler shifting, the lines of each transition are spread over a frequency range greater than 1.5 MHz. There are also present emission features which Zuckerman et al. (1971) have identified with the 110 -l11 transition of formic acid (HCOOH), which has a rest frequency of 1638.805 MHz. In view of some disagreement in the literature over the 16OH/18OH abundance ratio (Wilson and Barrett 1970; McGee et al. 1970), and of the baseline uncertainties in the spectra published in support of the HCOOH detection, we have obtained spectra of the two sources over the frequency range under discussion.

Extensive observations of the spectra of the decametric radio bursts for Jupiter have been made by Riihimaa, principally at frequencies between 18 and 23 MHz and with frequency resolution of 50 kHz. These showed much fine frequency-time structure in the bursts but pointed to the need for higher frequency resolution and greater antenna sensitivity. This paper reports the results of observations made of the Jupiter bursts between February and April, 1972, using the Llanherne low frequency telescope (Ellis,).

On 1973 March 22 a radio event was observed above the east limb of the Sun with the Culgoora radioheliograph operating at both 80 and 160 MHz. The first stage of this event, a type I storm closely associated with a rising prominence, offers a new insight into the nature of this phenomenon. This storm was followed immediately by a moving type IV burst – the first burst of this kind for which two-dimensional observations are available at two frequencies. The relation between these two stages may help explain the ‘missing hour’ in observations of another moving type IV burst known as ‘Westward Ho’.

Over the past century the techniques and progress of optical astronomy have depended largely on the performance and limitations of the photographic plate. The sort of observations we can make, the faintest limits to which they have been carried and the design of telescopes and instruments have all been circumscribed by the available plates. Over the next decade we will see our emulsions gradually replaced for most applications by one or more of a variety of photo-electric imaging systems now under development.

There are three non-thermal sources in the Large Magellanic Cloud which are recognized as supernova remnants. They are N49, N63A and N132D in Henize’s catalogue; a summary of their observing history is given by Westerlund and Mathewson (hereinafter referred to as ‘WM’). They are rather important to our knowledge of supernovae, as there are only four galactic supernova remnants (Cas A, the Crab, the Cygnus Loop and Vela) whose distances are known approximately from independent evidence. Since the distance to the LMC is well-known, the distance to sources in it is also known quite accurately.

A major crisis facing theoretical nuclear astronomers and physicists today is the apparently very low flux of neutrinos emitted by the Sun. Davis et al. report a measurement of 1.5 ± 1 s.n.u. (1 s.n.u. = 10−36 capture/Cl37/sec) which is a factor of 6 or so smaller than the theoretically predicted values. Numerous suggestions, often quite bizarre, have been made to account for the low flux, but so far no convincing explanation has been offered – see Fowler.

The variable X-ray source in the direction of the Small Magellanic Cloud (SMC), SMC X-1 (2U 0115-73) was discovered by Leong et al. (1971). X-ray eclipses with a period of 3.8927 ± 0.0010 days were subsequently reported by Schreier et al. (1972). Identification of the X-ray source with SK 160, star number 160 in the list of Sanduleak (1968), was proposed by Webster et al. (1972) on the basis of the similarity of its spectrum with that of the optical counterpart of Cyg X-1.

Low frequency radio waves propagating in the interstellar medium are attenuated through absorption by thermal electrons, the optical depth being given by

where f is the radio frequency in MHz, the emission measure in cm-6 pc, and Te the electron temperature.

The majority of OH/IR stars have been identified as M-type Mira variables, but there are a few cases where the stars have been identified as M supergiants or late-type semi-regular variables. A large number of OH sources have also been discovered with the 1612 MHz OH characteristics of OH/IR stars but no apparent optical or infrared counterparts. In several cases the velocities of these unidentified sources (OH stars) have been outside the velocity range of the neutral hydrogen distribution, suggesting that some of these sources may represent a population with a higher velocity dispersion than Population I objects (Kerr and Bowers 1974a, b). The lack of infrared and optical counterparts may indicate that the sources are quite distant, since identified OH/IR stars are often bright infrared objects. A large-scale 1612 MHz sky survey has therefore been initiated to study the galactic distribution and kinematics of the OH stars and to investigate the possibility that they may represent an older population of stars (Bowers et al. 1974).

The effective Rayleigh number, in the solar convection zone, soon reaches a value of the order of 106 and, although considerable progress has been made in the numerical integration of the basic system of differential equations at high Rayleigh number, it is of interest to investigate more fully the application of asymptotic methods to such a problem.

When a star of mass ≳ 2M⊙ collapses there does not appear to exist any physical mechanism to prevent total gravitational collapse, unless in some miraculous way the star always manages to blow off enough mass for it to settle down into a stable neutron star or white dwarf configuration. General relativity is needed in order to handle the ultimate situation, and the theory predicts a critical radius ρ = 2m (in units such that G = c = 1) at which the coordinates in the Schwarzschild solution

become invalid.

A Skylark rocket (SL727) carrying an X-ray astronomy experiment prepared by the University of Adelaide and Tasmania (UAT) was launched from Woomera at 0030 UT on July 10, 1970. The Large Magellanic Cloud (LMC) was detected during the flight, and the recent observation of structure within the Cloud is confirmed. In particular, the data support the suggestion of X-ray emission from the 30 Doradus (Tarantula) Nebula.

Cen X-3 and Her X-1 are the only two X-ray binaries which are known to pulsate periodically (at 4.8s and 1.2s respectively) in the X-ray region. The latter was identified with a fourteenth magnitude light and spectrum variable HZ Her, which was subsequently found to exhibit 1.24 second optical pulsations during certain phases. The possibility that Cen X-3 may prove to be as interesting an object optically has resulted in a wide spread search for its optical counterpart.