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More or Less - Polls, nuns, life partnersSunday, 3rd May 2015 20:00 - BBC Radio 4More or Less looks at the supposed increase in catholic nuns, polling data and the best way to find a life partner.... Read more: OU on the BBC: More or Less - Polls, nuns, life partners
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Wastemen: The Home FrontMonday, 4th May 2015 23:00 - BBC Two
Wartime Farm Episode 2Tuesday, 5th May 2015 11:00 - Yesterday
More or Less - Polls, nuns, life partnersAvailable until Wednesday, 27th April 2016 14:15More or Less looks at the supposed increase in catholic nuns, polling data and the best way to find a life partner.... Read more: OU on the BBC: More or Less - Polls, nuns, life partners
OU on the BBC: Frozen PlanetA stunning portrait of life at the poles, presented by David Attenborough Read more: OU on the BBC: Frozen Planet
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
Ratio, proportion and percentagesFrom politics to cookery, ratios, proportions and percentages are part of everyday life. This... Try: Ratio, proportion and percentages 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
Stars can necessarily be observed only at a distance. This unit introduces the...
Stars can necessarily be observed only at a distance. This unit introduces the Hertzsprung–Russell diagram, an essential tool in understanding the nature of stars. You should have some understanding of the basic stellar properties of luminosity and temperature in order to get the most from the unit.
After studying this unit you should be able to:
- describe and comment on the main features of a Hertzsprung-Russell diagram of stars in general, and of stars in a cluster;
- outline a broad model of stellar evolution based on the observed properties of large numbers of stars, and describe how stars of different initial mass might evolve;
- describe the effects of interstellar material on starlight, and outline some of the processes by which such material might be a source of electromagnetic radiation.
- Current section: Introduction
- Learning outcomes
- 1 The Hertzsprung-Russell diagram
- 2 Observing through the interstellar medium
- 3 Summary
- 4 Questions
We can study the individual properties of individual stars, such as photospheric temperature, luminosity, radius, composition and mass. If we wish to understand more about stars and obtain some insight into their evolution, we need to look at the overall distribution of stellar properties. We would like to know the answers to such questions as ‘Can stars have any combination of these properties?’ and ‘How many stars are there of each type?’ We can potentially learn a lot more about the stars if we compare them, but what should be the basis of our comparison? We certainly want to use intrinsic properties, such as luminosity, and not properties that depend on the distance to the star, such as the flux density received on Earth. Also, as an initial step, we want to avoid properties that are well removed from what we actually observe. In this unit we look at probably the most important diagram in stellar astronomy, the Hertzsprung-Russell diagram, and how it is used to identify the main classes of stars.
This unit is an adapted extract from the course