We describe a major Anglo-Australian project to undertake a UKST Ha survey of the Southern Galactic plane, Magellanic clouds and selected regions. The survey will use a new 12 × 12 inch monolithic Hα interference filter of high specification and Tech Pan film which offers significant advantages over other emulsions due to its peak sensitivity at Ha and its extremely fine grain, high resolution, exceptional DQE, excellent imaging and low noise. A survey of unprecedented area coverage, depth and resolution should result, superior to any previous optical survey of ionised gas in the galaxy. It is certain to lead to exciting new discoveries and new avenues of research.

The time scales in the s process appears to be an approriate aspect to discuss at the occasion of Roberto's 70th anniversary, the more as this subject has been repeatedly addressed during the 20 years of collaboration between Torino and Karlsruhe. The two chronometers presented in this text were selected to illustrate the intense mutual stimulation of both groups. Based on a reliable set of accurate stellar (n, γ) cross sections determined mostly at FZK, the Torino group succeeded to develop a comprehensive picture of the various s-process scenarios, which are most valuable for understanding the composition of the solar system as well as for the interpretation of an increasing number of astronomical observations.

Hα emission is one of the most prominent features of young stellar objects in the optical range, and importantly, the equivalent width (EW) of Hα emission [EW(Hα)] is used to characterise an evolutionary stage of young stars. The aim of this work is to identify and study the stellar objects with variable EW(Hα) in the young stellar cluster IC 348. We performed photometric and slit-less observations at several epochs in order to reveal the variable objects. Significant variability of EW(Hα) was found in 90 out of 127 examined stars. From all epochs of observations, 32 objects were classified as CTT (classical T Tauri) and 69 as WTT (weak-line T Tauri) objects. The fraction of the variables in these samples is ~60%. We also identified 20 stellar objects, which showed not only a significant variability of the EW, but which also change their apparent evolutionary stage (CTT ⇆ WTT). For six stars, Hα line was observed in both emission and absorption.

The analysis of data obtained over a wide wavelength range (from X-ray to mid-infrared) has shown that Hα activity and the measure of its variability are in good agreement with the activity of stellar objects measured with its other parameters, such as X-ray radiation and the mass accretion rate. The EW(Hα) differs not only between objects at different evolutionary stages, but also between variable and non-variable objects. The variables in the CTT and WTT samples are more active than non-variables although they have almost the same evolutionary age. Another distinct difference between these variables and non-variables is their average masses. The variables from both CTT and WTT samples are noticeably more massive than non-variables. Our data confirm the assumption made for other star formation regions that the decay of accretion activity occurs more slowly for more massive CTT objects. Apparently, a similar trend is also present in WTT objects, which are at a later stage of evolution. The variability of the stellar objects, which change their evolutionary classes (CTT ⇆ WTT), at least in a fraction of them, is due to the fact that they are close binaries, which affects and modulates their Hα emission activity.

NASA’s all-sky survey mission, the Transiting Exoplanet Survey Satellite (TESS), is specifically engineered to detect exoplanets that transit bright stars. Thus far, TESS has successfully identified approximately 400 transiting exoplanets, in addition to roughly 6 000 candidate exoplanets pending confirmation. In this study, we present the results of our ongoing project, the Validation of Transiting Exoplanets using Statistical Tools (VaTEST). Our dedicated effort is focused on the confirmation and characterisation of new exoplanets through the application of statistical validation tools. Through a combination of ground-based telescope data, high-resolution imaging, and the utilisation of the statistical validation tool known as TRICERATOPS, we have successfully discovered eight potential super-Earths. These planets bear the designations: TOI-238b (1.61$^{+0.09} _{-0.10}$ R$_\oplus$), TOI-771b (1.42$^{+0.11} _{-0.09}$ R$_\oplus$), TOI-871b (1.66$^{+0.11} _{-0.11}$ R$_\oplus$), TOI-1467b (1.83$^{+0.16} _{-0.15}$ R$_\oplus$), TOI-1739b (1.69$^{+0.10} _{-0.08}$ R$_\oplus$), TOI-2068b (1.82$^{+0.16} _{-0.15}$ R$_\oplus$), TOI-4559b (1.42$^{+0.13} _{-0.11}$ R$_\oplus$), and TOI-5799b (1.62$^{+0.19} _{-0.13}$ R$_\oplus$). Among all these planets, six of them fall within the region known as ‘keystone planets’, which makes them particularly interesting for study. Based on the location of TOI-771b and TOI-4559b below the radius valley we characterised them as likely super-Earths, though radial velocity mass measurements for these planets will provide more details about their characterisation. It is noteworthy that planets within the size range investigated herein are absent from our own solar system, making their study crucial for gaining insights into the evolutionary stages between Earth and Neptune.

In conjunction with the Australian Government's Spectrum Management Agency, experimental tests have been carried out to determine the susceptibility of the Molonglo Observatory Synthesis Telescope (MOST) to interference from terrestrial transmitters. The motivation for the tests was to reconcile the conflicting requirements of the MOST, which is committed to an extensive survey of the southern sky at 843 MHz, with the commercial use of the 825–845 MHz band, which is being prepared for sale. The tests show that the far sidelobe gain of the MOST, relative to an isotropic antenna is generally less than 1, and that an appropriate interference criterion would be that in-band interference irradiance should not exceed −173 dBWm−2. This value is similar to that considered by the International Telecommunications Union to be detrimental to radio astronomy continuum observations at nearby frequencies.

Detecting and mitigating radio frequency interference (RFI) is critical for enabling and maximising the scientific output of radio telescopes. The emergence of machine learning (ML) methods capable of handling large datasets has led to their application in radio astronomy, particularly in RFI detection. Spiking neural networks (SNNs), inspired by biological systems, are well suited for processing spatio-temporal data. This study introduces the first exploratory application of SNNs to an astronomical data processing task, specifically RFI detection. We adapt the nearest latent neighbours (NLNs) algorithm and auto-encoder architecture proposed by previous authors to SNN execution by direct ANN2SNN conversion, enabling simplified downstream RFI detection by sampling the naturally varying latent space from the internal spiking neurons. Our subsequent evaluation aims to determine whether SNNs are viable for future RFI detection schemes. We evaluate detection performance with the simulated HERA telescope and hand-labelled LOFAR observation dataset the original authors provided. We additionally evaluate detection performance with a new MeerKAT-inspired simulation dataset that provides a technical challenge for machine-learnt RFI detection methods. This dataset focuses on satellite-based RFI, an increasingly important class of RFI and is an additional contribution. Our SNN approach remains competitive with the original NLN algorithm and AOFlagger in AUROC, AUPRC, and F1-scores for the HERA dataset but exhibits difficulty in the LOFAR and Tabascal datasets. However, our method maintains this accuracy while completely removing the compute and memory-intense latent sampling step found in NLN. This work demonstrates the viability of SNNs as a promising avenue for ML-based RFI detection in radio telescopes by establishing a minimal performance baseline on traditional and nascent satellite-based RFI sources and is the first work to our knowledge to apply SNNs in astronomy.

We construct an idealised universe for didactic purposes. This universe is assumed to consist of absolute Euclidean space and to be filled with a classical medium which allows for sound waves. A known solution to the wave equation describing the dynamics of the medium is a standing spherical wave. Although this is a problem of classical mechanics, we demonstrate that the Lorentz transformation is required to generate a moving solution from the stationary one. Both solutions are here collectively referred to as “spherons”. These spherons exhibit properties which have analogues in the physical description of matter with rest mass, among them de Broglie like phase waves and at the same time “relativistic” effects such as contraction and a speed limit. This leads to a theory of special relativity by assuming the point of view of an observer made of such spheronic “matter”. The argument made here may thus be useful as a visualisation or didactic approach to the real universe, in which matter has wave-like properties and obeys the laws of special relativity.

The unprecedented imaging power of James Webb Space Telescope (JWST) provides new abilities to observe the shapes of objects in the early Universe in a way that has not been possible before. Recently, JWST acquired a deep field image inside the same field imaged in the past as the Hubble Space Telescope (HST) Ultra Deep Field. Computer-based quantitative analysis of spiral galaxies in that field shows that among 34 galaxies for which their rotation of direction can be determined by the shapes of the arms, 24 rotate clockwise, and just 10 rotate counterclockwise. The one-tailed binomial distribution probability to have asymmetry equal or stronger than the observed asymmetry by chance is $\sim$0.012. While the analysis is limited by the small size of the data, the observed asymmetry is aligned with all relevant previous large-scale analyses from all premier digital sky surveys, all show a higher number of galaxies rotating clockwise in that part of the sky, and the magnitude of the asymmetry increases as the redshift gets higher. This paper also provides data and analysis to reproduce previous experiments suggesting that the distribution of galaxy rotation in the Universe is random, to show that the exact same data used in these studies in fact show non-random distribution, and in excellent agreement with the results shown here. These findings reinforce consideration of the possibility that the directions of rotation of spiral galaxies as observed from Earth are not necessarily randomly distributed. The explanation can be related to the large-scale structure of the Universe, but can also be related to a possible anomaly in the physics of galaxy rotation.

We report the discovery of a bow-shock pulsar wind nebula (PWN), named Potoroo, and the detection of a young pulsar J1638$-$4713 that powers the nebula. We present a radio continuum study of the PWN based on 20-cm observations obtained from the Australian Square Kilometre Array Pathfinder (ASKAP) and MeerKAT. PSR J1638$-$4713 was identified using Parkes radio telescope observations at frequencies above 3 GHz. The pulsar has the second-highest dispersion measure of all known radio pulsars (1 553 pc cm$^{-3}$), a spin period of 65.74 ms and a spin-down luminosity of $\dot{E}=6.1\times10^{36}$ erg s$^{-1}$. The PWN has a cometary morphology and one of the greatest projected lengths among all the observed pulsar radio tails, measuring over 21 pc for an assumed distance of 10 kpc. The remarkably long tail and atypically steep radio spectral index are attributed to the interplay of a supernova reverse shock and the PWN. The originating supernova remnant is not known so far. We estimated the pulsar kick velocity to be in the range of 1 000–2 000 km s$^{-1}$ for ages between 23 and 10 kyr. The X-ray counterpart found in Chandra data, CXOU J163802.6$-$471358, shows the same tail morphology as the radio source but is shorter by a factor of 10. The peak of the X-ray emission is offset from the peak of the radio total intensity (Stokes $\rm I$) emission by approximately 4.7$^{\prime\prime}$, but coincides well with circularly polarised (Stokes $\rm V$) emission. No infrared counterpart was found.

Dodson and Hedeman discovered an unexpected effect in the occurrence of solar proton events as revealed by polarcap absorption (PCA). When the 48 events in Bailey’s Catalog of the Principal PCA Events, 1952-1963 are distributed with the phase of the moon there is a gap of several days near full moon; also, many more events occur when the moon waxes than when it wanes. Dodson and Hedeman did not find similar, apparent departures from random distribution either with a mean solar rotation period of 27.3 days or for solar flare events. They concluded that ‘at the present time it is not clear whether the 29.5 day “effect” is related to the sun or the moon or is only a statistical accident’.

On 1971 January 24 a 3B flare at 18° N., 49° W. was associated with the acceleration of protons to relativistic energies; it was one of the rare events recorded by ground-level neutron monitors. Excellent radio coverage was obtained with single-frequency radiometers in the range 1000-9400 MHz, and at Culgoora with the 8-8000 MHz spectrograph and the 80 MHz radioheliograph. At the Earth relativistic protons and electrons arrived very promptly from the flare, whose site was near the foot of the nominal interplanetary field line which connects to the Earth.

Observations of the composite radio source which includes the catalogued components 1209-52 and 1209-51 (Bolton et al. 1964) have been obtained at frequencies 629, 1410, and 2650 MHz with the 210-ft Parkes telescope. The observations at the highest frequency are shown in Figure 1. The isotherms of full-beam brightness temperature correspond to the single polarization direction shown within the circle representing the half-intensity beamwidth. The polarization vectors (unbroken lines) along the two ridges represent 15-25% linear polarization. The intrinsic angles of polarization, derived from the 1410 and 2650 MHz observations, are represented by the broken lines. They are perpendicular to the magnetic field if the radiation is synchrotron. The corresponding rotation measures (Gardner and Whiteoak 1963) range between +17 and +36 rad. m-2 along the eastern ridge, and between —14 and —4 on the western side.

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).

Many of the X-ray pulsars for which X-ray lightcurves have been presented in the literature exhibit asymmetric emission beams. We postulate the existence of an off-centre magnetic dipole field embedded in the rotating neutron star and show that such a field leads to varying rates of matter transfer between an accretion dise and the neutron star surface, over a rotation period. Assuming that the accretion rate onto the surface is simply related to the luminosity, we show that most of the observed asymmetries can be accounted for by this mechanism.

Prompted by recent moves to ask the International Astronomical Union to redefine the System III rotation period, we have used all available dekametric observations from 1951 to 1975 and new analysis methods in an attempt to improve our estimate of the Jovian dekametric rotation period.

We have developed water vapour radiometers (WVRs) for the Australia Telescope Compact Array that are capable of determining signal path-length fluctuations by virtue of measuring small temperature fluctuations in the atmosphere using the 22.2-GHz water vapour line for each of the six antennae. By measuring the line-of-sight variations of the water vapour, the induced path excess and thus the phase delay can be estimated and corrections can then be applied during data reduction. This reduces decorrelation of the source signal. We demonstrate how this recovers the telescope's efficiency as well as how this improves the telescope's ability to use longer baselines at higher frequencies, thereby resulting in higher spatial resolution. A description of the WVR hardware design, their calibration, and water vapour retrieval mechanism is given.

The Physics Department at the University of Otago, Dunedin, New Zealand, has over the past three years commenced a research and teaching programme in astronomy and astrophysics. Observing facilities now include two metric wave meridian transit telescopes at a site 6 km from Dunedin and a 16-inch optical telescope, formerly at Mt John, which is now sited 4 km from Dunedin at the Signal Hill observatory built by the University’s Surveying Department for geodetic work.

The traditional approach to the extragalactic distance scale rests on a pyramid of primary, secondary and tertiary indicators of increasing range and decreasing accuracy. This multi-step procedure, fraught with the danger of cumulative errors, has led in recent years to two main, widely diverging scales: the ‘long’ scale (Sandage and Tammann 1974, 1975, 1976) implying a Hubble constant and the ‘short’ scale (de Vaucouleurs 1978, 1979; de Vaucouleurs and Bollinger 1979; de Vaucouleurs and Peters 1981; de Vaucouleurs et al. 1981) leading to H0 ≃ 100. Several authors have already shown that the long scale rests on very precarious foundations (Capaccioli and Fasano 1980, de Vaucouleurs 1981, Hanes 1980); counter arguments have been offered in its defence and to criticize the short scale (Tammann, Sandage and Yahil 1979, Sandage and Tammann 1982). For want of a conclusive test a consensus was still lacking.

An analysis has been made of events recorded in one year from the direction of the active galaxy Centaurus A using the Buckland Park UHE gamma-ray telescope. No statistically significant excess was observed over this period. Data collected between 1984 and 1989 show evidence for an excess of events from this direction at shower sizes in the range of 2 × 105 to 5 × 105 particles.

Clumpy, intense wave packets observed in situ in the Jovian and terrestrial electron foreshocks, and in the Earth’s auroral acceleration zone, point to the existence of non-linear plasma turbulence in these regions. In non-linear turbulence, wave packets collapse to short scales and high fields, stopping only when coherent wave-particle interactions efficiently dissipate the energy in the waves. The purpose of this paper is to examine the shortest scales and highest fields achieved during collapse in a strongly magnetised plasma, and identify parts of the solar system where the magnetised aspects of wave collapse are important.