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Stars can necessarily be observed only at a distance. Comparing stars is a 16-hour free course that introduces the HertzsprungRussell 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 course, 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
- 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!
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 course 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 OpenLearn course is an adapted extract from the Open University course S282.
Copyright & revisions
Originally published: Wednesday, 16th March 2016
Last updated on: Wednesday, 16th March 2016
- 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.
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