New observations of the Magellanic Stream were made in December 1976 with the 64-m radio telescope at the Parkes Observatory of CSIRO. The ridges of H I emission of the Stream were traced from near its tip at ℓ = 90°, b = -40° to the Magellanic Clouds. This was the first time that the total length of the Stream was observed with the one system (only possible from the southern hemisphere) and with high spatial (15’ of arc) and velocity (4 km s-1) resolution. The results of this survey are presented in Figures 1 and 2 and the main features are listed below.

Hodge 11 (= SL 868) is a red, globular-like cluster (V ≅ 12.1, B—V = 0.62), situated on the east side of the LMC about 5 kpc projected distance from its centre (Gascoigne 1966). It was included in a programme to study the chemical evolution of the LMC by determining ages and metal abundances for a number of its clusters. Figure 1 shows a preliminary colour-magnitude diagram, found from four AAT plates calibrated with the AAT two-channel photometer. The choice of the radius, 1′.37 (23 pc), within which the stars were measured, was guided by the surface photometry of the cluster described later (Figure 3). But while it makes the number of “clean” stars inside the radius rather small, those outside it are too unlikely to be cluster members. As yet the calibration extends only to V = 19.6, and the nature of the cluster cannot be determined unambiguously. But Figure 1 already shows an unusual feature, in the very blue colour of the group of stars at V ≅ 19, B—V = 0.60, which on the usual interpretation would point to a metal abundance possibly lower than any yet encountered.

Over the past ten years, there has been considerable interest in the infrared continua of quasars, however few published colours exist in the literature. The only major compilation of infrared data out to 2.2 μ is that of Oke et al. (1970). The intrinsic faintness of the sources prevented the acquisition of significant high quality data. This situation is not expected to remain static for very long. The recent introduction of new high sensitivity InSb detectors has made it possible for a large number of sources to be measured, and published data is expected to increase significantly over the next few years.

Rich clusters of galaxies are a common feature of the large-scale structure of the Universe. Those studied so far, show striking regularities with

1. (a) a smooth radial gradient of number density.

2. (b) ’isothermal’ distributions, which according to Bahcall (1975) have a scatter of only ±15% in the size of their characteristic core radii.

3. (c) their limiting structural diameters are ~50 Mpc (cf. Abell, 1975), if they are identified with superclusters.

4. (d) the magnitude of the velocity dispersion about their centres is generally 600-1000 km s-1, and the velocities are cpnsistent with a gaussian distribution (Yahil and Vidal, 1976; also Faber and Dressier, 1976).

5. (e) The extreme velocities are generally within ±3000 km s-1, and for Coma are ∼2400 km s-1 (Tifft and Gregory, 1976).

6. (f) elliptical galaxies tend to predominate near the centre, spirals in the surrounding loose groups.

We present here preliminary results of further radio and optical work being carried out on the Molonglo Deep Survey (Robertson 1977a, b, c) which reaches a density of ∼ 20,000 sources per sterad at a limiting flux density of 84 mJy at 408 MHz in three small areas of sky at declinations -20° and -62°. The position errors range from 4 to 15 arc sec r.m.s. depending on flux density. Optical identifications are being made by G. W. using the Palomar Sky Survey in the -20° region and the ESO and SRC surveys in the -62° region. In the latter case, where only one colour is available more accurate positions are necessary to identify QSO candidates. The Fleurs synthesis telescope is being used to obtain accurate positions.

The eighth magnitude star HD 101065 is an extremely peculiar star with a unique spectrum characterized by numerous strong lines of the rare earths and the absence, or at least a remarkable weakening, of the lines of the iron group (Cowley et al. 1977). Besides the lanthanides only yttrium, zirconium, calcium and barium are definitely present in the atmosphere in substantial quantities. The evidence for the presence of lithium and strontium is subject to some doubt since these elements are represented only by one or two reasonably strong lines, which is insufficient for a positive identification in a spectrum as complex as that of HD 101065. The evidence for the presence of other elements is the subject of a critical examination in a recent paper by Cowley et al. (1977). The effective temperature of the star is about 6100 K (Przybylski, 1977) which is substantially lower than the temperature of any known Ap star. However, the effective temperature of HD 101065 is still subject to controversy (Wegner, 1976).

The metal content of stars (and galaxies) is of great interest as it relates to the theories of element formation, and through these to the history of our galaxy, the frequency of supernovae, the star formation rate and even the quasar rate. The kinematics and metallicity of stars have been correlated in a theory of formation of the galaxy by Eggen et al. (1962). Alternate theories (Unsold 1969) have also been proposed. Much work has gone into isolating individual metal deficient stars and determining their abundances, and also the abundances for stars in clusters.

IRC + 10216, a bright infrared late type carbon star, is observed to have millimetre range line emission of the species 12CO, 13CO, CS, C2H, HC3N, CN, HCN, SiS and SiO in an extended envelope around the central infrared sources. The infrared emission arises from two concentric dust shells around the star: an inner 0”.2 arc radius shell of 600 K and optically thick, i.e. radiating as 600 K black body, and an outer shell 1″.0 arc radius at 375 K and optically thin for λ ≳ 2μ. A model explaining the line emission in terms of infrared pumping between the two lowest vibrational levels, first proposed by Morris (1975a) for IRC + 10216, was used to calculate antenna temperatures for various rotational transitions of HC3N; since there is a prima facie agreement between the calculated and observed values for HC3N we have attempted the same calculation for DC3N.

Many cold molecular clouds have been detected as a result of their association with dense optical obscuration. The HII region RCW 36 is contained within a prominent dust lane extending several degrees along a line of almost constant right ascension (see e.g. Rodgers et al. 1960). By means of H2CO and OH observations we have found that this lane is associated with a dense elongated molecular cloud.

Although it is well known that HII regions are present in the innermost regions of the Galaxy their kinematics are still not fully understood. In one study Pauls et al. (1976) surveyed with a beamwidth of 3′ arc the 10 GHz recombination line emission in directions within 15′ arc of the nuclear radio source Sgr A. They found that the emission velocities varied from position to position within the range -50 to + 50 km s-1but appeared to lack any overall pattern. In contrast, we have recently observed the recombination line emission from the galactic centre region with a beamwidth of 4′.5 arc, and find strong evidence of ordered motions near the galactic nucleus.

Ammonia was the first interstellar molecule with more than two atoms to be discovered (Cheung et al. 1968). Since that time it has been observed in many HII regions and dark clouds (Mayer et al. 1973; Morris et al. 1973; Cheung et al. 1973; Kaifu et al. 1975). The molecule has a rich rotation-inversion spectrum with about 10 transitions in the range 23-25 GHz. Each line has hyperfine structure which permits, in principle, the determination of optical depths, filling factors and excitation. Unfortunately line brightness temperatures are low (<1 K) so that a low-noise receiving system and long integration times are required to exploit these possibilities.

Soft X-ray photographs of the Sun taken from the manned Skylab satellite (Vaiana et al. 1973) gave, not the earliest, but perhaps the most graphic evidence that the solar corona is patchy. During the Skylab mission (May 1973 to February 1974), the solar corona as usually envisaged covered only 80% of the Sun (Bohlin 1977). The areas lacking a ‘dense’ corona are called coronal holes (Withbroe al. 1971; Waldmeier 1975).

The magnetic structure in the source region of a type II burst and along the path of the type II disturbance has remained an enigma despite over 20 years of radio observations of the Sun (see e.g. reviews by Wild and Smerd (1972) and McLean (1974)). This paper describes the first radioheliograph observations of a type II burst near coronal magnetic structures depicted by soft X-ray pictures. It will be shown that three separate lanes in a type II burst are associated with three separate source regions each located almost radially above a soft X-ray loop. To explain these observations a model is derived in which a wide-fronted m.h.d. disturbance travels from the flare explosion along magnetic field lines and then intersects successively with three coronal streamer structures each located above a soft X-ray loop. An estimate of the magnetic flux density along the soft X-ray loops is obtained from the velocity of the m.h.d. disturbance.

On 1975 August 22 an outburst above the west limb of the Sun was observed with the Culgoora radioheliograph at 43, 80 and 160 MHz. The first stages of the event included intense type III/V bursts followed by a type II burst with multiple, fundamental and harmonic bands and herringbone structure. While the type II burst was still in progress a moving type IV burst appeared. It was eventually observed out to a distance of more than 3 R⊙. This was the first moving type IV burst observed with the two-dimensional radioheliograph operating at three frequencies; as such it provides valuable constraints on models of moving type IV sources.

In this paper we model mathematically the propagation of galactic cosmic-rays in the solar cavity and study the effects of changing the physical parameters; in particular the radius of the cavity. We assume spherical symmetry with heliocentric distance r, momentum p and work in terms of F0(r, p) the mean distribution function with respect to momentum; it is related to JT the mean differential intensity w.r.t. energy by JT = p2F0. The boundary is at r = rb beyond which the galactic spectrum prevails; there is free escape of particles incident on rb from within, and the distribution is steady state.

The energy passing through the boundaries of a convective zone in a star, in an outward radial direction per second, must in total be equal to the luminosity of the star, provided of course that this zone does not encompass nuclear energy producing regions. If, in an endeavour to establish the nature of the convective motions in this zone, a section of the zone is modelled by considering steady cellular convection in a horizontal layer of Boussinesq fluid, it is on the basis of an average energy flux being imposed. Moreover, the sum of the conductive and convective heat fluxes is represented by the Nusselt number, which is specified and constant for the zone.

Semiconvection is the name given to a situation that arises in the evolution of large-mass main-sequence stars and lower-mass horizontal-branch stars, in which a layer forms where almost all of the heat flux is transported by radiation, but where slow convection is required to redistribute a stably stratified solute (e.g. helium). For a general discussion on semiconvection, see Spiegel (1969). The main problem is to determine the correct relationship between the solute distribution and the temperature gradient in the inhomogeneous layer. Ledoux (1947) and Schwarzschild and Harm (1958) have proposed two very different prescriptions. Since theory and experiment indicate that the Schwarzschild-Harm (SH) prescription is correct for the onset of convection (in the form of overstability), Spiegel (1969) has proposed that SH are correct. However, neither observation (oceanographic or laboratory) nor theory precludes a substantial deviation from the SH prescription as applied to finite amplitude semiconvection. The observational evidence is only readily applicable to stars if Pr≳, 1, where Pr is the Prandtl number of the fluid. In fact, Pr≪ 1 in stars. It is shown below that if one could have stars in which Pr ≳ 1, then the SH prescription would probably be wrong, and the Ledoux criterion might then be nearer to being correct. In the real situation (Pr≪ 1), observations or experiments are lacking and theory alone does not provide an unequivocal answer to the problem. This paper does not attempt a complete discussion of the problem, and a more detailed report will be submitted elsewhere. Some aspects of the problem have already been discussed in the context of the giant planets (Stevenson and Salpeter 1977).

The deep interiors of cold, degenerate stars consist of a mixture of elements, either because of primordial inhomogeneities or because of incomplete nuclear burning. However, most existing calculations for the cooling of such bodies (subsequent to any nuclear burning) assume that the only source of luminosity is the heat content of the star. An additional (and potentially much larger) energy source is available if the elements have limited mutual solubility below some temperature. The resulting differentiation and gravitational settling can dramatically decrease the rate of cooling, enhance the number of (potentially) observable low luminosity bodies, and may deplete the atmosphere of heavy elements (if substantial mixing between the atmosphere and deep interior occurs). The observational evidence for these phenomena is equivocal at present.

A number of authors (Reddish, 1968, 1969, Reddish and Wickramasinghe 1969) have stressed the importance for star formation of the role of condensation of H2, onto solid grains inside the cool dark regions of a large interstellar cloud. However, although the thermodynamic consequences of the existence of grains have been extensively studied, the dynamical implications have received little attention. Solid grains of course do not possess a thermal pressure as their gaseous counterpart does, neither do they directly experience the magnetic fields which thread the ions and electrons of the gas cloud. The grains therefore, as soon as they are formed, are free to fall toward their common centre of mass, relatively unrestricted by the constraints on the gas cloud.

A major area of difficulty in the cosmogony of the solar system is understanding how a large number of small planetesimals, which have condensed from the primordial gas, can aggregate into the ordered planetary system present today. Theories involving aggregation within a gaseous disc [e.g. Cameron (1973)] suffer the common difficulty that the particles, once condensed, are no longer supported by the radial gas pressure gradient and spiral rapidly in towards the Sun. Most of the planetesimals are dragged in to the central body in times several orders of magnitude less than would be required for larger bodies to accrete (Goldreich & Ward 1973).