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In this paper, we present the stationary axisymmetric configuration of a resistive magnetised thick accretion disc in the vicinity of external gravity and intrinsic dipolar magnetic field of a slowly rotating black hole. The plasma is described by the equations of fully general relativistic magnetohydrodynamics (MHD) along with the Ohm’s law and in the absence of the effects of radiation fields. We try to solve these two-dimensional MHD equations analytically as much as possible. However, we sometimes inevitably refer to numerical methods as well. To fully understand the relativistic geometrically thick accretion disc structure, we consider all three components of the fluid velocity to be non-zero. This implies that the magnetofluid can flow in all three directions surrounding the central black hole. As we get radially closer to the hole, the fluid flows faster in all those directions. However, as we move towards the equator along the meridional direction, the radial inflow becomes stronger from both the speed and the mass accretion rate points of view. Nonetheless, the vertical (meridional) speed and the rotation of the plasma disc become slower in that direction. Due to the presence of pressure gradient forces, a sub-Keplerian angular momentum distribution throughout the thick disc is expected as well. To get a concise analytical form of the rate of accretion, we assume that the radial dependency of radial and meridional fluid velocities is the same. This simplifying assumption leads to radial independency of mass accretion rate. The motion of the accreting plasma produces an azimuthal current whose strength is specified based on the strength of the external dipolar magnetic field. This current generates a poloidal magnetic field in the disc which is continuous across the disc boundary surface due to the presence of the finite resistivity for the plasma. The gas in the disc is vertically supported not only by the gas pressure but also by the magnetic pressure.
We describe the High-Precision Polarimetric Instrument-2 (HIPPI-2) a highly versatile stellar polarimeter developed at the University of New South Wales. Two copies of HIPPI-2 have been built and used on the 60-cm telescope at Western Sydney University’s (WSU) Penrith Observatory, the 8.1-m Gemini North Telescope at Mauna Kea and extensively on the 3.9-m Anglo-Australian Telescope (AAT). The precision of polarimetry, measured from repeat observations of bright stars in the SDSS g′band, is better than 3.5 ppm (parts per million) on the 3.9-m AAT and better than 11 ppm on the 60-cm WSU telescope. The precision is better at redder wavelengths and poorer in the blue. On the Gemini North 8-m telescope, the performance is limited by a very large and strongly wavelength-dependent TP that reached 1000’s of ppm at blue wavelengths and is much larger than we have seen on any other telescope.
The detection of fireballs streaks in astronomical imagery can be carried out by a variety of methods. The Desert Fireball Network uses a network of cameras to track and triangulate incoming fireballs to recover meteorites with orbits and to build a fireball orbital dataset. Fireball detection is done on-board camera, but due to the design constraints imposed by remote deployment, the cameras are limited in processing power and time. We describe the processing software used for fireball detection under these constrained circumstances. Two different approaches were compared: (1) A single-layer neural network with 10 hidden units that were trained using manually selected fireballs and (2) a more traditional computational approach based on cascading steps of increasing complexity, whereby computationally simple filters are used to discard uninteresting portions of the images, allowing for more computationally expensive analysis of the remainder. Both approaches allowed a full night’s worth of data (over a thousand 36-megapixel images) to be processed each day using a low-power single-board computer. We distinguish between large (likely meteorite-dropping) fireballs and smaller fainter ones (typical ‘shooting stars’). Traditional processing and neural network algorithms both performed well on large fireballs within an approximately 30 000-image dataset, with a true positive detection rate of 96% and 100%, respectively, but the neural network was significantly more successful at smaller fireballs, with rates of 67% and 82%, respectively. However, this improved success came at a cost of significantly more false positives for the neural network results, and additionally the neural network does not produce precise fireball coordinates within an image (as it classifies). Simple consideration of the network geometry indicates that overall detection rate for triangulated large fireballs is calculated to be better than 99.7% and 99.9%, by ensuring that there are multiple double-station opportunities to detect any one fireball. As such, both algorithms are considered sufficient for meteor-dropping fireball event detection, with some consideration of the acceptable number of false positives compared to sensitivity.
Radiative transfer is essential for obtaining information from the spectra of astrophysical objects. This volume provides an overview of the physical and mathematical background of radiative transfer, and its applications to stellar and planetary atmospheres. It covers the phenomenology and physics of early-type and late-type stars, as well as ultra-cool dwarf stars and extrasolar planets. Importantly, it provides a bridge between classical radiative transfer and stellar atmosphere modelling and novel approaches, from both theoretical and computational standpoints. With new fields of application and a dramatic improvement in both observational and computational facilities, it also discusses the future outlook for the field. Chapters are written by eminent researchers from across the astronomical disciplines where radiative transfer is employed. Using the most recent observations, this is a go-to resource for graduate students and researchers in astrophysics.
The Murchison Widefield Array (MWA) is an open access telescope dedicated to studying the low-frequency (80–300 MHz) southern sky. Since beginning operations in mid-2013, the MWA has opened a new observational window in the southern hemisphere enabling many science areas. The driving science objectives of the original design were to observe 21 cm radiation from the Epoch of Reionisation (EoR), explore the radio time domain, perform Galactic and extragalactic surveys, and monitor solar, heliospheric, and ionospheric phenomena. All together $60+$ programs recorded 20 000 h producing 146 papers to date. In 2016, the telescope underwent a major upgrade resulting in alternating compact and extended configurations. Other upgrades, including digital back-ends and a rapid-response triggering system, have been developed since the original array was commissioned. In this paper, we review the major results from the prior operation of the MWA and then discuss the new science paths enabled by the improved capabilities. We group these science opportunities by the four original science themes but also include ideas for directions outside these categories.
We provide our first experience of Astronomy training as an in-service training of teachers of Science in Primary schools, and teachers of Geography, Physics and Mathematics in Secondary Schools necessitated due to lack of Astronomy specific training in their teacher training programs. The hands-on training was conducted in collaboration with the IAU Commission 46 Working Group program of Network of Astronomy Schools Education (NASE). Experiences from both face to face and virtual sessions conducted during the Covid19 period and in preparation of a major African solar eclipse, are discussed.
In this contribution I will briefly introduce the concept and objectives of the Open Universe Initiative, as well as describe the first steps of its implementation by Brazil, in conjunction with the United Nations Office for Outer Space Affairs (UNOOSA), aiming to encourage new interested parties to join the Initiative.
We propose a set of modern and stimulating activities related to the teaching of Astronomy orientated to high school or university students using smartphones. The activities are: a) the experimental simulation of asteroid light curves including the determination of the period of rotation of asteroids, b) the experimental simulation of exoplanet detection by transit method, c) the experimental simulation of stellar distances using parallax and d) the use of virtual and augmented reality.
Youths and kids in Indonesia since almost two decades ago have been showing significant increase of interest in space sciences, especially astronomy. One of the main factors is due to the annual event of National Science Olympiad which includes Astronomy as the subject. The increasing level of public interest, especially younger generation on astronomical events, such as eclipses, moon sightings, meteor showers has been constantly observed from time to time. Being aware that Astronomy course does not included in primary and secondary education level’s curricula, teachers are somewhat desperate and are not capable to play role as clearing house in science related to space. The IAU Network of Astronomy for School Education Network (IAU-NASE) course was started in 2016 in Machung University, East Java as the pilot project in Indonesia. The course has attracted significant interest from teachers and university staff, especially in East and Middle Java Provinces. Being confident with the enthusiasm of teachers who expressed that NASE course could fulfil their needs to teach and instruct students in a very efficient way, it was organized consecutively at Bandar Lampung, Lampung Province in 2018 and 2019 (hosted by Institut Teknologi Sumatera) and in 2020 at Bandung, West Java Province (hosted by Institut Teknologi Bandung). The most recent NASE course on 21–23 August 2020, conducted in on-line mode, was attended by 74 participants, although primarily aimed at 15 School teachers, and was quite successful. The on-line observational activity turned out to be the most impressive session for the participants. We report and review four years of IAU NASE courses in Indonesia, with various documentation and brief analysis of the positive impact to the teachers and instructors attitude in teaching astronomy at secondary level of education.
LLAGN are very important objects for studying as they are found in a large fraction of all massive galaxies. Nevertheless this topic needs more investigation as fraction of LLAGN in all AGN are much more higher than fraction of researches dedicated to LLAGN among all AGN studies. The goal of our work is checking out X-ray properties of LLAGN. For this purpose we created a sample of LLAGN by selecting most prominent LLAGN from literature and analyzed their X-ray spectral properties. As a result, we obtained 12 LLAGN and for 8 of them XMM X-ray observations are available. The spectra from one XMM camera, PN, were fitted with power law + absorption of neutral hydrogen. In the current report we present the previous results of this study. We plan to increase numbers of objects in our future studies.
Of all the questions that Man asks himself about the Universe, the one concerning the possibility of the existence of an extra-terrestrial life form, and even more of an extra-terrestrial civilization, is probably the most fascinating. We cannot answer it today, but we can imagine the implications for the human species and its future in the Universe.
This project is designed for children under 18 years that have to frequently visit hospitals or that have to endure long-term hospital stays. The aims are to entertain these children and their families, to increase their scientific culture, and to promote scientific vocations. So far we have visited one hospital in Mexico City bringing astronomy to the patients and their families. We have developed five hands-on activities and one musical activity that ensures that all the children can participate independently of their conditions. We plan to expand this project to other hospitals and other cities in the country. Our next challenge is to start virtual visits to hospitals.
This article presents a didactic experience in teacher training carried out in the province of Santa Fe, Argentina. The training was carried out on the occasion of a total solar eclipse taking place in this region on July 2, 2019. Prior to this event, the authors, members of NASE, developed training meetings of the Ministry of Education of Santa Fe , on topics of Astronomy. From these workshops, participants of all educational levels with different specialties, carried out with their students school science activities where they applied Astronomy with an interdisciplinary perspective. In this way, the eclipse became an event that made possible an enrichment of astronomical education in the region.
Sunspot observations, normally made with small telescopes during the last four centuries, should be considered a world heritage for many reasons including purely scientific aspects and other cultural and social reasons. Here, these aspects are briefly reviewed.
I discuss the second IAU Strategic Plan for the decade 2020–30 in the context of the overall evolution of the IAU in recent past decades. This article shows how the IAU has evolved dramatically since WW2. It is hardly recognizable in terms of its original organization and goals of a century ago. What was once an inward-looking body engaged purely with the procedures of astronomical research is now a dynamic and outward-looking organization, interacting with people, especially students and the public.
A large part of this success must be attributed to the IAU’s unique body of individual members, whose number has grown strongly in recent decades. It is the individual members, especially through the Commissions and Working Groups, who have promoted these enormous changes in the outlook of the Union. This is a model for other scientific unions to follow, and especially for the work to promote the careers of women in science, for promoting the careers of young astronomers, for bringing students into astronomy or into science in general, for helping people with disabilities to have careers in astronomy, for engaging with the public, and for helping to develop astronomy and science in developing countries.
Looking to the future, the IAU’s new Strategic Plan for the years 2020 to 2030 has five major goals for the coming decade: 1. The IAU leads the worldwide coordination of astronomy and the fostering of communication and dissemination of astronomical knowledge among professional astronomers. 2. The IAU promotes the inclusive advancement of the field of astronomy in every country. 3. The IAU promotes the use of astronomy as a tool for development in every country. 4. The IAU engages the public in astronomy through access to astronomical information and communication of the science of astronomy. 5. The IAU stimulates the use of astronomy for teaching and education at school level.
Future developments will also be engaging with the large number of amateur astronomers and helping to promote astro-tourism, which is perhaps the new frontier now growing rapidly around the world. The Strategic Plan is a blueprint for forging a social revolution in astronomy and for using astronomy as a tool for building a progressive society.
Influence of astronomy education, in other disciplines, can give some possible explanation even in the history field. We propose to link astronomy, history and heritage through Big Data, without a telescope.
If we look to the Dacian Draco flag we can find a similitude with Draco constellation and that was a little bit intrigue. In the era of digitalization we can use computers to see back in time.
In the context of the European Middle Ages as the period roughly covering from the 5th to the 15th centuries, the astronomical records are rarery found in scientific treatises. At least, not until the 15th century. A few surprinsing examples in which the observations were recorded in a particularly original way on stone are found. In this poster we will shortly review the only four cases in which this occurred in Europe.
This paper provides a brief overview of the many facets of astronomy education and heritage, and how the IAU stimulates them. Activities range from training in astronomy through scientific meetings and schools for young astronomers, to using astronomy as a tool for development and for stimulating science education at school level. Communicating astronomy with the public and engaging in outreach activities with children to inspire curiosity is yet another way of how astronomy can help build a literate society and install a sense of global citizenship. The involvement of many people at all levels is key to success.