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An overview of active galaxies
Active galaxies provide a prime example of high energy processes operating in the...
Active galaxies provide a prime example of high energy processes operating in the Universe. This unit gives an overview of active galaxies, including the supermassive black holes that power the engines at their centres, and the emission processes by which we detect and study them. It also gives practice in mathematical techniques for analysing data and theoretical models.
By the end of this unit you should be able to:
- recognise the terminology which is used to describe the properties and behaviour of active galactic nuclei (AGN);
- manipulate numbers, algebraic symbols and mathematical functions in equations.
- Current section: Introduction
- Learning outcomes
- 1 Meet your first active galactic nuclei
- 2 Black holes: a reminder
- 3 AGN reside at the centres of galaxies
- 4 Black holes at the centres of ordinary galaxies
- 5 Distances in extragalactic astronomy
- 6 The key questions
- 7 Continuum emission processes
- 7.1 Blackbody radiation
- 7.2 Free-free radiation
- 7.3 Polarization of electromagnetic radiation
- 7.4 Faraday depolarization
- 7.5 Emission from spiralling electrons: synchrotron radiation
- 7.6 Producing synchroton radiation in a laboratory
- 7.7 Radiation detection
- 7.8 Example 2 and questions
- 7.9 Compton scattering
- 8 Basic properties and historical perspective
- 9 Summary
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An overview of active galaxies
This unit begins by studying evidence leading to our basic hypothesis that active galactic nuclei (AGN) are accreting, supermassive black holes. It also covers some physics of radiation which you will need to be able to interpret the observed emission of AGN, and includes an examination of AGN.
You will be studying a young subject and there are fundamental issues which are still being vigorously debated by the experts and are subject to current research activity. Consequently, it is not possible to give clear definitive explanations of all aspects of the subject.
You may already have become accustomed to reading unfamiliar words and phrases. In this unit, you will not only encounter new and specialised vocabulary, you will meet ideas which are currently being shaped and tested. Do not be dismayed if you fail to immediately grasp the underlying principles behind some of the material you will read: it is possible no-one has yet elucidated them!
This unit is from our archive and is an adapted extract from The energetic universe (S381) which is no longer taught by The Open University. If you want to study formally with us, you may wish to explore other courses we offer in.
This is an extract from an Open University course which is no longer available to new students. If you found this interesting you could explore more free Physics and Astronomy courses or view the range of currently available OU Physics and Astronomy courses.
Copyright & revisions
Originally published: Tuesday, 19th April 2011
- Creative-Commons: The Open University is proud to release this free course under a Creative Commons licence. However, any third-party materials featured within it are used with permission and are not ours to give away. These materials are not subject to the Creative Commons licence. See terms and conditions. Full details can be found in the Acknowledgements section.
- This site has Copy Reuse Tracking enabled - see our FAQs for more information.
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