from The Open University
Alternatively you can skip the navigation by pressing 'Enter'.
Wastemen: One Man's Rubbish...Wednesday, 6th May 2015 00:00 - BBC Two ScotlandThe value of waste has never been higher - but it's not just financial value; the Wastemen are aware of the emotional... Read more: Wastemen: One Man's Rubbish, One Man's Treasure
Wartime Farm Episode 3Wednesday, 6th May 2015 11:00 - Yesterday
Thinking Allowed: Gentrification and division of domestic labourWednesday, 6th May 2015 16:00 - BBC Radio 4
Wastemen: One Man's Rubbish...Wednesday, 6th May 2015 23:50 - BBC Two
Wastemen: The Home FrontAvailable until Thursday, 4th June 2015 00:15In the first of the series, Christmas is coming. And the most magical time of the year brings with it enormous... Read more: Wastemen: The Home Front
International Year of Light - Translation ProjectBe part of an international project to get our International Year of Light animation translated... Read more: International Year of Light - Translation Project
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
Facilitating learning in practice[BETA ] Are you interested in mentorship or looking to develop your mentorship skills? In... Try: Facilitating learning in practice 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