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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Gamma-ray evidence for cosmic-ray sources

Rogers, Martin John January 1988 (has links)
The origin of cosmic-rays is one of the long-standing problems in astro physics. In recent years, strong evidence has been found that certain classes of object contain and are able to accelerate particles to high energies. In this thesis the origin problem is addressed in two different ways. Firstly, two different regions of the Galaxy are studied using γ-ray observations from the COSB satellite combined with atomic and molecular gas measurements. The Vela region contains a pulsar and a supernova remnant and is particularly valuable location for cosmic-ray studies because of its proximity, the association of the two objects, and the intensity of the γ -ray flux it produces. At greater longitudes, the region around the peculiar object η Carinae is also studied. It is rich in potential sources of cosmic rays including active stars and a spiral arm seen at a tangent at l ~ 282º .Analysis of the Vela region reveals strong evidence for cosmic ray production at all energies observed by COSB. The supernova remnant seems the most likely candidate, but the possibility of the pulsar itself producing some of the particles cannot be ruled out. The excess γ -ray emission from around η Carinae does not appear correlated with the active stars but seems to becoming predominantly from the spiral arm. This is the first time evidence has been presented for cosmic-ray acceleration by the spiral shock in a particular, known spiral arm which is observed as a feature in the gas. The γ -rays are produced in the gas clouds associated with this arm. The second approach to the cosmic-ray origin problem involves a model for cosmic-ray production in supernova remnants and is used in association with a Monte-Cailo simulation of their occurrence in the Galaxy. Unlike earlier models (Bhat et al 1987), the motion of the Sun is also taken into account and the supernova explosions occur mainly in spiral arms. The results are in the form of a time sequence of energy density values and tire compared in detail with (^10)Be results. It is found that the model accounts for the long-term rise in the concentration of this radioisotope and does not predict large excursions from the mean energy density that beset older models. Thus the cosmic ray production by supernova remnants seems to be consistent with the radioisotope data.
2

The design of an International School of Astronomy & Astro-Tourism Centre in Sutherland, Karoo

Noeth, Graeme January 2014 (has links)
M. Tech. Architecture (Professional) / Over the last decade, South Africa (RSA) has experienced a substantial growth in the field of astronomy and astrophysics. Post 2005, the largest optical telescope in the Southern hemisphere, known by its acronym, SALT, was constructed in RSA. It is expected that by 2024, this country will host the largest array of radio telescopes in the world, the Square Kilometre Array (SKA). It could be argued that RSA is at the forefront of modern cosmological research. This exponential growth in the field of astronomy has resulted in local astronomical bodies and universities falling behind in astronomy education. This provides a unique opportunity to strengthen the latter. The aim of this dissertation is to design an International School of Astronomy and Astro-Tourism Centre. The proposed building aims to introduce a unique facility in the Northern Cape that would benefit the field of astronomy worldwide. The proposed facility is situated at the South African Astronomical Observatory (SAAO) in Sutherland. It is nested within the South-west-embankment of the mountain, currently hosting the Southern Africa Large Telescope (SALT). The resultant design takes on a linear building typology with radial aspects to document astronomical events. The project investigates the semi-arid Karoo climate and how the resultant architecture reacts to harsh environmental conditions.

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