Explain — 2 marks
Astronomers have discovered that our Sun is approximately 4.6 billion years old and is currently in the middle of its life cycle. Scientists predict that in about 5 billion years, the Sun will undergo significant changes that will affect all planets in our solar system, including Earth.
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Explain what will happen to the Sun as it reaches the end of its main sequence phase.
[2 marks]
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- {'mark': 1, 'description': 'The Sun will expand / swell / increase in size'}
- {'mark': 1, 'description': 'The Sun will become a red giant / increase in brightness or luminosity'}
Calculate — 3 marks
A astronomy student is observing the Sun and studying how stars change over their lifetime. The Sun is currently in its main sequence stage and has been burning hydrogen in its core for approximately 4.6 billion years. Scientists predict the Sun will remain in this stable stage for another 5 billion years before expanding into a red giant.
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Calculate the total length of time the Sun will spend in its main sequence stage. Give your answer in standard form.
[1 mark]
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The Sun's core temperature is approximately 1.5 × 10^7 K. When the Sun becomes a red giant, its core temperature will increase to about 1.0 × 10^8 K. Calculate how many times hotter the red giant core will be compared to the current core temperature.
[1 mark]
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The Sun's luminosity (brightness) is approximately 3.8 × 10^26 W. A red giant star has a luminosity of 1.9 × 10^28 W. Calculate how many times brighter the red giant is than the Sun.
[1 mark]
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Define — 2 marks
Astronomers studying distant stars have observed that many stars exist in binary systems, where two stars orbit around a common centre of mass. As these stars age and evolve, they eventually reach the end of their lives. Understanding the key terms used to describe stellar objects and their properties is essential for interpreting astronomical observations.
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Define what is meant by a 'red giant' star.
[1 mark]
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Define what is meant by the 'main sequence' when referring to a star's life cycle.
[1 mark]
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