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Thinking Allowed: Global clothing and poverty, fur inheritance in PolandMonday, 30th March 2015 00:15 - BBC Radio 4Laurie Taylor and guests discuss fast fashion and hand-me-downs regarding the links to class and poverty. Read more: Thinking Allowed: Global clothing and poverty, fur inheritance in Poland
Timewatch: StonehengeAvailable until Friday, 24th April 2015 11:00Two of Britain’s leading archaeologists and world-renowned experts on Stonehenge, Professor Tim Darvill and Geoff... Read more: OU on the BBC: Timewatch - Stonehenge
Turn your bank holiday into a badged holidayWhat are your plans for the long weekend? DIY? A trip to a windswept beach? Why not take your... Read more: Turn your bank holiday into a badged holiday
Take the photographic memory testCan you capture scenes just by looking at them? Find out with our photographic memory test. Launch now: Take the photographic memory test
Early years team work and leadershipThis unit explores aspects of teamwork and leadership for early years practitioners. Try: Early years team work and leadership 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