from The Open University
Alternatively you can skip the navigation by pressing 'Enter'.
Life: PlantsFriday, 12th February 2016 10:00 - Eden EdenAs ingenious as any animal... Read more: Life: Plants
Life: PlantsFriday, 12th February 2016 16:00 - Eden Eden
More or Less: Selfies, sugar daddies, schoolchildren and public spendingFriday, 12th February 2016 16:30 - BBC Radio 4
Life: PlantsFriday, 12th February 2016 22:00 - Eden Eden
The London Markets: The Fruit And Veg Market: Inside New SpitafieldsAvailable until Sunday, 13th March 2016 00:40The fruit and veg trade in England was once a closed world dominated by traditional British costermonger families.... Read more: The London Markets: The Fruit And Veg Market: Inside New Spitafields
The Bottom Line: Winter 2015-16: Customer ServiceAvailable for over a year
Thinking Allowed 2016: Weather forecasting, Young people and politicsAvailable for over a year
Thinking Allowed 2016: Consumerism, Work-life balanceAvailable for over a year
OpenLearn Live: 12th February 2016The last prince of an independent Wales; then more free learning across the day. Read more: OpenLearn Live: 12th February 2016
OpenLearn Live: 11th February 2016The first king to unite Wales into a single kingdom; working with Richard Nixon; making love last... Read more: OpenLearn Live: 11th February 2016
Landschaftliche VielfaltGerman regions and landscapes, local traditions and the notion of Heimat are at the centre of... Try: Landschaftliche Vielfalt now
Succeed with maths – Part 1If you feel that maths is a mystery that you want to unravel then this free course is for you. It... Try: Succeed with maths – Part 1 now
Active galaxies provide a prime example of high energy processes operating in the Universe. This free course 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 free course 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
- Keep on learning
Study this free course
Enrol to access the full course, get recognition for the skills you learn, track your progress and on completion gain a statement of participation to demonstrate your learning to others. Make your learning visible!
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 free course includes adapted extracts 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
Last updated on: Monday, 15th October 2012
- 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 and our FAQs section.
- This site has Copy Reuse Tracking enabled - see our FAQs for more information.
If you enjoyed this, why not follow a feed to find out when we have new things like it? Choose an RSS feed from the list below. (Don't know what to do with RSS feeds?)
Remember, you can also make your own, personal feed by combining tags from around OpenLearn.
All our alternative formats are free for you to download, for more information about the different formats we offer please see our FAQs. The most frequently used are Word (for accessibility), PDF (for print) and ePub and Kindle to download to eReaders*.
*Please note you will need an ePub and Mobi reader for these formats.