1. 1
   An amateur astronomer is comparing the appearance of different stars through a telescope on a clear night, noting differences in their colour and brightness, and researching how these observable properties relate to the physical processes occurring inside each star.

   (a)

   An amateur astronomer observes two stars through a telescope one evening: one appears distinctly blue-white, and the other appears distinctly red. Which statement correctly explains why the stars appear as different colours?

   [1 mark]

   • AA star's colour is related to its surface temperature, with hotter stars appearing more blue-white and cooler stars appearing more red
   • BA star's colour depends only on its distance from Earth, not on any physical property of the star itself
   • CA star's colour is related to its surface temperature, with hotter stars appearing more red and cooler stars appearing more blue-white
   • DAll stars are the same colour, and any apparent difference is caused entirely by Earth's atmosphere

   (b)

   The astronomer wants to classify each star according to its colour to estimate its surface temperature. Which of the following pairs correctly matches a colour with its relative surface temperature?

   [1 mark]

   • AYellow stars are always the hottest of all stars
   • BRed stars are hotter than yellow stars, which are hotter than blue-white stars
   • CBlue-white stars are hotter than yellow stars, which are hotter than red stars
   • DAll stars have the same surface temperature regardless of colour

   (c)

   Explain how the brightness of a star observed from Earth can be a misleading indicator of how much light the star actually emits, and describe how absolute magnitude helps address this problem.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   An astrophysics lecturer is describing the complete life cycle of stars to first-year university students, covering both the stages followed by stars of similar mass to the Sun and the different path taken by stars of much greater mass.

   (a)

   An astrophysics lecturer is describing the life cycle of a star similar in mass to the Sun to a group of first-year students. What is the very first stage in the evolution of such a star, before nuclear fusion begins?

   [1 mark]

   • AA red giant
   • BA nebula, a large cloud of gas and dust
   • CA white dwarf
   • DA main sequence star

   (b)

   The lecturer explains that after billions of years on the main sequence, a Sun-like star will expand enormously. What is this expanded stage called, and what happens to the star immediately after this stage ends?

   [1 mark]

   • AThe star becomes a red giant, then immediately forms a black hole
   • BThe star becomes a white dwarf, then eventually forms a red giant
   • CThe star becomes a nebula, then eventually forms a red giant
   • DThe star becomes a red giant, then eventually forms a white dwarf

   (c)

   State, in the correct order, the four stages in the evolution of a star of similar mass to the Sun, from its very beginning to its final stable stage.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A science journalist is preparing a feature article for a popular science magazine, explaining to a general audience how the eventual fate of a massive star differs dramatically from the fate awaiting our own Sun many billions of years from now.

   (a)

   A science journalist is writing an article comparing the eventual fate of the Sun with the fate of stars that have a much greater mass, such as those many times heavier than the Sun. Describe how the evolution of a star with a mass much larger than the Sun differs from the stages followed by a Sun-like star.

   [3 marks]

   (b)

   Explain why stars with a much greater mass than the Sun evolve and 'die' more quickly than Sun-like stars, despite starting with a much larger supply of nuclear fuel.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   An observatory is designing a new public display for visitors that uses a Hertzsprung-Russell diagram to help explain how astronomers classify stars and interpret their properties from a single chart, based on temperature and luminosity.

   (a)

   An observatory is creating a public display featuring a Hertzsprung-Russell (HR) diagram, which plots stars according to their luminosity (or absolute magnitude) against their surface temperature. Describe the main components and layout of the HR diagram, including where the main sequence, red giants and white dwarfs are typically found on it, and explain what the position of a star on this diagram reveals about its properties.

   [6 marks]

   (b)

   Using the HR diagram, explain how the movement of a star's position across the diagram over its lifetime reflects the stages of stellar evolution described earlier, comparing the path taken by a star similar in mass to the Sun with that of a much more massive star.

   [6 marks]

   Total for question 4: 12 marks

End of questions