Recently, Unno has proposed a new method for constructing models of convective non-grey atmospheres, making two substantial improvements to the mixing-length theory of Böhm-Vitense. His method, based on the variational technique of Glansdorff-Prigogine, enables the determination of the eddy-size and is no longer dependent on an ad hoc assumption of a constant mixing-length to scale height ratio. It also takes into account the effects of non-grey radiative transfer.

During 1971/72 the radioheliograph at Culgoora, N.S.W. was used to observe 30 bright galaxies at 80 MHz.

In the first decade or so of 21 cm studies the galactic spiral structure problem was treated in a very straightforward manner. A simple velocity-distance transformation was used to derive the locations of the spiral arms from the radial velocities of the main features on the 21 cm profiles. Some well-known diagrams were obtained in this way.

The ratio of the mass density in visible galaxies to the upper limit for the HI mass density determined from the lack of continuous Ly-α absorption in QSO spectra is 3 × 104. Thus, if galaxies form by condensation from an intergalactic medium, the process must be extremely efficient. Although no absorption due to a continuous distribution of intergalactic HI has been detected, many QSOs have been discovered that have absorption lines in their spectra, which have redshifts very different from the emission lines, and may be produced in clouds of integalactic HI. As would be expected if this were the case, the proportion of QSOs with absorption lines in their spectra is greatest for those which have large emission line redshifts. Another possibility, especially for those absorption lines in redshift systems with Zabs nearly equal to Zem , is that the absorption lines are produced in clouds surrounding the QSO.

Spectrometers give information on the chemical composition and physical properties of celestial objects. The Earth’s atmosphere restricts the observable spectra to windows in the absorption. Most of these windows are less than one octave wide. To increase the amount of information gained, it is necessary to increase the resolution of the spectrometers. With the advent of balloons, rockets and spacecraft, it is possible to make observations free from atmospheric absorption and it is possible to gain more information by increasing the bandwidth of spectrometers. This paper describes an infra-red Fourier transform spectrometer. The interferometer has a bandwidth of over one decade, from 500 to 5,000 cm-1, with a maximum resolution of 10 cm-1. The resolution can be electronically controlled. There are no absorbing or refracting parts in the interferometer and the resolution is limited by mechanical considerations.

In his studies of the temperature fluctuation in the solar photosphere P. R. Wilson came to the conclusion that, in order to explain Edmond’s r.m.s. intensity fluctuation distribution against heliocentric angle, one is led, using two dimensional solutions for the equation of radiative transfer, to the existence of a sharp temperature fluctuation of about 660 K r.m.s. at a depth of 250 km below τ5000 = 0.03 and that this temperature fluctuation decreases sharply in the next 70 km. There also seems to be an indication that there exists a second temperature fluctuation maximum at a depth of approximately 100 km below the first one.

The third Uhuru catalogue of X-ray sources (Giacconi et al. 1974) contains X-ray source positions given to a much higher precision than was previously available and this fact has given considerable impetus to the search for optical and radio counterparts. Many such identifications have now been made and confirmed, e.g. by discoveries of correlated variability.

As has been previously stated (van der Borght) the lengths l1, l2, l3 and l4 are functions of and so a discussion of these lengths is in fact a discussion of the f’s. For a first approach to a determination of these f’s, a standard Vitense2 model of the convection zone—with mixing length l, is used. We assume that l = H. The variables we need are kz, which are the vertical wave number associated with the characteristic eddy, the average vertical velocity, and the average (non-dimensional) temperature fluctuation. These quantities are approximated, using the following relations

The radio source, Cen A, is large and complex with many peaks in the brightness distribution over an area about 4 x 10 degrees. The peculiar elliptical galaxy NGC 5128 lies between the two strong inner radio brightness peaks and is centred on a weaker central radio source. This radio source is in the centre of the dust lane which divides the galaxy and may be related to the infrared, X-ray and γ-ray sources.

While Uhuru’s contribution to X-ray astronomy in the energy range 1 – 20 keV (and more particularly 2 – 10 keV) has been most impressive, it remains true that satellite observations outside this energy range, and particularly at energies above 20 keV which are also accessible to balloon-borne instrumentation, have been somewhat disappointing. We cannot forsee any likely marked improvement in this situation for at least four years and we believe therefore, that balloon-borne payloads can continue to contribute significantly to the study of hard X-ray sources.

Compact radio sources have been observed over several years at 2.3 GHz by interferometers of the NASA-JPL Deep Space Network with trans- or inter-continental baselines to study the secular behaviour of fine structure appearing in these sources. A comparison of the variation in flux density of components of diameter < 0.001 arcsec with the corresponding variation in total flux density of the source at the same frequency indicated that variations could be wholly ascribed to components of this order of magnitude.

It has been often suggested that the solar granulation is essentially a turbulent convective phenomenon. It is then worthwhile to investigate steady state, finite-amplitude convection in the outer layers of the solar convection zone. On the basis that the convection zone is turbulent, we will define an eddy viscosity; and for the present we will consider only the first 300 km of the convection zone. This value is predicted by van der Borght using an asymptotic analysis of convection at high Rayleigh number—provided we assume the horizontal dimension of the cellular pattern to be ˜1000 km.

Evidence has recently been put forward that Jupiter might be modulating the intensity of cosmic radiation observed at the earth (Pizzella and Venditti 1973; Cini-Castagnoli et al. 1973). It therefore seemed worthwhile to analyse underground meson data in Jovian time for any evidence of an effect at the higher energies over a complete orbital period.

A 30 MHz radio telescope has recently been completed at Fleurs, N.S.W. There has been a need for a high resolution sky survey to be carried out in the Southern Hemisphere at a frequency intermediate between 19.7 MHz (Shain et al.) and 85.7 MHz (Mills et al). One particular reason lies in the fact that some HII regions which are seen in absorption against the galactic background at 19.7 MHz and in emission at 85.7 MHz may match the background temperature at 30 MHz. If the temperature of such a region has been found by other means, the 30 MHz temperature of the portion of the Galaxy beyond it is determined irrespective of conditions nearer the observer, since the two temperatures must be equal.

To date the Culgoora radioheliograph has recorded seven continuum bursts simultaneously at its three operating frequencies of 160, 80 and 43 MHz. In every case the radio emission is found to originate from stationary sources whose heights increase with decreasing frequency. The implications of these new observations are discussed below.