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Topic outline

 

  • Time: 8 hours
    Level: Introductory

 
 

Introduction

  • Introduction Resource
  • For astronomers, the Sun is fascinating because it is our nearest star. By studying the Sun, they can gain an insight into the workings of the other millions of stars that are visible in the night sky....
 

1 Observing the Sun

  • Observing the Sun Resource
  • Never look directly at the Sun, either with the unaided eye or through spectacles, binoculars or a telescope. You risk permanently damaging your eyes if you do so.
  • 1.1 The Sun at visible wavelengths Resource
  • The Sun is seen as a blindingly bright, yellow object in the sky. The part of the Sun that you normally see is called the photosphere (meaning ‘sphere of light’); this is best thought of as the ‘surface’...
  • 1.2 Beyond visible light Resource
  • During the twentieth century, astronomers extended their capabilities by developing telescopes and detectors that were sensitive to radio waves, microwaves, infrared and ultraviolet radiation, X-rays and...
  • 1.3 The invisible Sun Resource
  • Figure 7 shows an image of the Sun, taken when a huge prominence was visible (bottom left). The image was recorded using instruments that are sensitive to ultraviolet radiation rather than visible...
 

2 Inside the Sun

  • 2 Inside the Sun Resource
  • To account for its brightness and activity, the Sun must contain a power source. However, the nature of that power source was a great puzzle in the nineteenth and early twentieth centuries. Fossil records...
 

3 Measuring the Sun

  • 3.1 Angular size Resource
  • The image shown in Figure 1 at the start of this unit (repeated above), was taken during a total eclipse of the Sun, in which the Moon blocked out light from the Sun's photosphere, enabling the chromosphere...
  • 3.2 Angular size, actual size and distance Resource
  • The angular size of an object is determined uniquely by its actual size and its distance from the observer. For an object of fixed size, the larger the distance, the smaller the angular size. For objects...
 

4 Unit summary

 

5 End-of-unit questions

 

References and Acknowledgements

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