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A History of Ideas - Buddhism's four Noble TruthsThursday, 2nd April 2015 12:04 - BBC Radio 4Naomi Appleton, Chancellor's fellow in Religious Studies at the University of Edinburgh, explores the Buddha's Four... Watch now: OU on the BBC: A History of Ideas - Buddhism's four Noble Truths
Joseph Fiennes on Romeo & JulietThursday, 2nd April 2015 20:00 - Sky Arts 1 HD
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Thinking Allowed: Citizenship ceremonies and family tiesMonday, 6th April 2015 00:15 - BBC Radio 4
Thinking Allowed: Citizenship ceremonies and family tiesAvailable until Thursday, 31st March 2016 09:15Laurie Taylor and guests discuss studies into citizenship and the links between family ties and stories. Read more: Thinking Allowed: Citizenship ceremonies and family ties
OU on BBC: A History of Ideas - Ayn Rand and selfishnessMorality and selfishness sound like opposites - but not according to the Russian-American... Watch now: OU on BBC: A History of Ideas - Ayn Rand and selfishness
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The business of footballWelcome to this free new OpenLearn course produced by The Open University working in partnership... Try: The business of football now
Succeed with maths – Part 1[BETA] If you feel that maths is a mystery that you want to unravel then this short 8-week course... Try: Succeed with maths – Part 1 now
Introduction to active galaxies
The field of active galaxies is recognised as one of increasing importance. But how do...
The field of active galaxies is recognised as one of increasing importance. But how do we know there are different kinds of galaxy? What are active galaxies? How are they powered? This unit examines the different types of active galaxy and looks at the crucial role of the active galactic nucleus and the energy source at its heart.
By the end of this unit you should be able to:
- explain how and why the optical spectrum of an active or starburst galaxy differs from that of a normal galaxy;
- explain how and why the broadband spectrum of an active or starburst galaxy differs from that of a normal galaxy;
- describe briefly the observed features of starburst galaxies and the four main classes of active galaxies (quasars, radio galaxies, Seyfert galaxies and blazars);
- understand the evidence that indicates the presence of a compact active galactic nucleus (AGN) in active galaxies;
- explain why an AGN should emit broad lines, narrow forbidden lines and continuous radiation;
- give an account of an accreting massive black hole as the engine of the AGN and relate its luminosity to the mass accretion rate;
- outline some of the outstanding problems relating to the evolution of active galaxies.
- Current section: Introduction
- Learning outcomes
- 1 Overview
- 2 The spectra of galaxies
- 3 Types of active galaxies
- 4 The central engine
- 5 Models of active galaxies
- 6 Outstanding Issues
- 7 Unit Summary
Introduction to active galaxies
Active galaxies provide a prime example of high-energy processes operating in the Universe. This unit introduces the evidence for activity from the spectra of some galaxies, and the concept of a compact active galactic nucleus as a unifying model for the observed features of several types of active galaxy. It also develops the key skill of applying arithmetic and simple algebra to solving scientific problems.
This course is an adapted extract fromt he course