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.

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.

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.

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.

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.

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.