Since 1965 we have been unravelling the curious properties of the intense 18 cm emission lines observed from OH molecules. We are still without a quantitative theory of the emission that might tie the threads together and provide guidelines for the observational work. The most plausible hypothesis is that we are dealing with naturally occurring interstellar gas masers. I want to present some of the latest evidence we have in favour of the maser action, and to indicate where it is inadequate. I will concentrate on work done in 1967, as the earlier work has been discussed in detail elsewhere.

In April of this year agreement was reached between the British and the Australian Governments to build a 150-inch telescope for observations of the southern sky.

The agreement specified that:

• (i) the telescope would be built at the Australian National University’s present site at Siding Spring Observatory;

• (ii) the expected cost was $11 million and the telescope would be built and operated on a 50-50 basis as between the two Governments;

• (iii) the telescope would be virtually a copy of the existing Kitt Peak 150-inch design. This was intended to save the time usually needed for the design of a new telescope and, as we shall see, it might lead to considerable savings in cost.

This paper describes a preliminary series of observations of the Sun made at a frequency of 80 MHz with the 3 km radioheliograph of the Culgoora Observatory. The instrument records, at one-second intervals, pictures of the solar image in the form of 60 (E-W) × 48 (N-S) points, each separated in angle by half the Rayleigh limit (2’ arc in the zenith). At the time of the present observations the instrument was incomplete in three main respects : (a) the facilities for recording opposite senses of circular polarization were not available; (b) the automatic image compensation for zenith-angle foreshortening was not available—hence the optical disk of the Sun appears elliptical; and (c) the phase and amplitude calibration procedures had not been fully established, resulting in a higher sidelobe level than that specified in the design—the effects are sometimes evident in the pictures as spoke-like brightenings.

The innermost Galilean satellite of Jupiter, Io, has been observed to strongly modulate the probability and intensity of Jupiter’s decametric emissions. The effect is most pronounced at frequencies greater than 30 MHz. Radiation occurs from two configurations of Jupiter and Io, the first when Io is 90° from superior geocentric conjunction (s.g.c.) and Jupiter’s longitude is near 120°, and the second when Io is 240° from s.g.c. and Jupiter’s longitude is near 230°.

This programme was undertaken because the preliminary observations of Beta Centauri with the Narrabri stellar interferometer (Hanbury Brown, Davis, Allen, and Rome) show that the correlation received is not consistent with that expected from a single star. The Lick Catalogue of Radial Velocities states that β Cen is a Bl II star. The Narrabri results are consistent with several models; in particular, it may be a double star with components of similar brightness, or it may have a very luminous, extended atmosphere or shell surrounding it. The latter possibility is perhaps unlikely on the spectroscopic evidence, as there are neither emission nor sharp absorption components in the spectral lines.

This paper presents a progress report on a programme of infra-red photoelectric photometry of the red giant sequences in some southern globular clusters. As measured in B and V these sequences are known to differ from cluster to cluster, at least one contributing factor being differential line-blanketing arising from variations in metal abundance. Observations in R and I should be substantially free of blanketing, and so enable us to eliminate this factor, clarifying the situation and making possible a more accurate transformation of the observations to the Mbol, log Tett plane. The difficulty of making this transformation has been a major obstacle in comparing observations and theory for cluster giants.

A coudé spectrogram of dispersion 150 µ/Å, exposed at the 74-inch reflector by D. S. Mathewson, reveals very many unusually sharp absorption lines due to ionized metals in the atmosphere of the B9 star HD 1909.

The stellar interferometer at Narrabri Observatory measures the angular diameter of hot, bright stars. It does this by matching the observed intensity correlation from two detectors, as a function of separation between the detectors, with that from a uniform disk (see Hanbury Brown et al.). When this measurement is taken in conjunction with experimental determinations of the monochromatic flux received at the Earth, the effective temperature of the star, Te, can be determined. However, if the star being observed is rotating rapidly, comparison with a uniform disk is of doubtful validity. Owing to its rotation the shape of the star will be distorted, and its effective temperature will vary over the surface (being apparently hotter at the poles). Therefore the measured angular diameter of the star will be different, and will change with the orientation of the star’s axis of rotation in the sky.

Recently the possibility has been raised of using general relativistic star clusters as models for quasi-stellar sources. The theory of static, spherically symmetric, collisionless star clusters has been developed within the framework of general relativity. In particular, analogues have been found of the Newtonian polytropic models and of Woolley’s truncated Maxwellian systems. However, in view of the importance of rotation on stability in relativistic astrophysical problems, it is of considerable interest to include the effect of rotation in relativistic stellar dynamics.

As shown recently by Y. Osaki super-massive stars with mass M < 3.5 × 105M⊙ can, in the absence of rotation, reach the hydrogen-burning main sequence before the onset of general relativistic instability. Such objects are then pulsationally unstable. A considerable simplification is introduced if one considers only very massive stars, for which the relative amplitude of the fundamental mode of oscillation is practically constant. This sets a lower limit of 104M⊙ to the mass that can be considered. The upper limit is also reduced to 2 × 105M⊙ if one neglects the relativistic correction. One necessary step in the study of non-linear oscillations of massive stars is to derive a differential equation for the adiabatic pulsations. The relativistic correction could be taken into account in the following way.

The equation of motion, derived from the basic Lagrangian equations for the conservation of momentum and the conservation of energy, for non-linear non-adiabatic radial oscillations of a pulsating star takes the form

Those solutions which have so far been obtained to the problem of a star with both rotation and a magnetic field have been for certain special cases, mostly time-independent. It is known that, except for stars with special rotation laws, a rotating star in hydrostatic equilibrium cannot maintain thermal equilibrium without generating slow meridional circulation of matter. It is also known that an axially symmetric field with no azimuthal component tends very strongly to keep the star in a state of isorotation, with the angular velocity constant along field lines. A magnetic field also tends to upset thermal equilibrium and produce meridional circulation. In the absence of rotation, an equilibrium poloidal field has recently been found for which there is no circulation. The present paper reports analogous equilibrium solutions for a star which is in uniform rotation.

A large part of the energy lost from interiors of evolving stars at temperatures greater than about 5 × 108°K is carried away by neutrinos. Three neutrino-producing reactions which have been incorporated in various evolutionary models are the photoneutrino process:

direct annihilation of electron-positron pairs:

and the plasma process:

The realization that the nuclei of planetary nebulae are stars which evolve with a time-scale of ~ 104 yr (O’Dell,Seaton) has prompted several theoretical investigations of the late stages of stellar evolution (Vila, Divine, L’Ecuyer). Vila has assumed that all nuclear burnings have ceased in these stars, and that the energy release is entirely gravitational. He showed that the inclusion of neutrino energy-loss processes based on the universal Fermi interaction of Feynman and Gell-Mann reduced the theoretical evolution time by two orders of magnitude to a value comparable with the observed time. His theoretical models, however, have effective temperatures greater than those observed by a factor of six.

In Table I are given photometric data and spectral classes for some OB stars in galactic longitudes 298°-306°. The data have been obtained using a photoelectric photometer on the Reynolds reflector and the Meinel spectrograph on the 100 cm reflector at Siding Spring. Numbers refer to an OB star catalogue in preparation.

In a recent paper Aizu and Tabara list 36 radio sources classified as supernova remnants (SNR). Some of these identifications are based on low-resolution radio data and are consequently unreliable. Using the Parkes 210-foot radio telescope at 635, 1410 and 2650 MHz (beamwidth 31′, 15′ and 8′.4 respectively), E. R. Hill and the author observed the seven sources listed in Table I. Of these seven, there is close agreement with Aizu and Tabara’s data only in the last one (3C396.1), and we agree with the SNR classification, with certain reservations, for only three of these sources.

The object of this contribution is to report the galactic background intensity at 2 and 3 MHz. The observation is an extension of earlier work which the noise temperatures at 50, 30, 20, 10 and 5 MHz were obtained at 65°N declination by means of identical antennas of beamwidth 70° between half-power points. As discussed in the earlier work, the temperatures were obtained separately in the ordinary and extraordinary modes, in order to account for the attenuation in the ionosphere.

It is a well established observational result that young stars exhibit differences in chemical composition. The differences are comparatively large. For example, some stars have metal abundances as high as 3/2 solar-value while others have abundances as low as 1/2 solar-value. The result was obtained through spectroscopic and photoelectric studies of stars with ages of a few times 108 yr and indicates that the interstellar medium is chemically heterogeneous at the present epoch.

Two-colour photoelectric light curves have been obtained for 9 SMC and 7 LMC variables, with periods in the range 1.24-6.61 days. Because of crowding problems, satisfactory observations could be obtained only for cepheids in the outer parts of the Clouds. The LMC cepheids are in the vicinity of NGC 1805-1818, in a field studied at Herstmonceux. The majority of those in the SMC are immediately south of NGC 362.

The Sydney University one mile cross-type radio telescope at the Molonglo Radio Observatory has been used to study the 30 Doradus nebula with high resolution (~3´ arc) at 408 MHz. This preliminary report compares these observations with Balmer line isophotes published by Faulkner. A description of the calibration procedures used in the present observations, an analysis of the various radio features in the 30 Doradus region, and a comparison with previous observations at other frequencies, will be described in a later paper.