1. 1
   A science communicator gives a talk explaining that the Sun is one of many billions of stars belonging to a huge galaxy, and that this galaxy is itself just one of many billions found throughout the observable Universe.

   (a)

   A science communicator explains that our Sun is just one of many billions of stars grouped together in a huge structure. What is this huge structure of billions of stars called?

   [1 mark]

   • AA galaxy
   • BA planet
   • CA nebula
   • DAn asteroid belt

   (b)

   What is the name of the galaxy that contains the Sun and the rest of our Solar System?

   [1 mark]

   • AAndromeda
   • BThe Milky Way
   • CThe Orion Nebula
   • DThe Kuiper Belt

   (c)

   State what a light-year is a measure of, and state the approximate value of one light-year in metres.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   An astronomer observes the light emitted from several distant galaxies and compares its wavelength with light emitted by similar sources on Earth, in order to investigate the motion of these galaxies relative to the Earth.

   (a)

   An astronomer observes light from a distant galaxy and notices that its wavelength appears to have increased compared with light emitted by a similar source on Earth. What is this observed increase in wavelength called?

   [1 mark]

   • ADiffraction
   • BBlueshift
   • CRedshift
   • DRefraction

   (b)

   What does the observation that light from distant galaxies is generally redshifted provide evidence for?

   [1 mark]

   • AThat distant galaxies are moving towards the Earth
   • BThat the Universe is shrinking
   • CThat all galaxies are stationary relative to the Earth
   • DThat the Universe is expanding

   (c)

   State the name of the widely accepted scientific theory that is supported by the observation of redshift in light from distant galaxies, and briefly explain what this theory suggests about the origin of the Universe.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A radio astronomy team detects microwave radiation of a specific frequency arriving uniformly from every direction in space, and investigates what this observation reveals about the origin and history of the Universe.

   (a)

   State the name of this radiation, and explain briefly why its discovery is considered strong evidence supporting the Big Bang Theory.

   [3 marks]

   (b)

   The team also uses the observed redshift of a distant galaxy to estimate its recession speed, and combines this with an estimate of its distance obtained from observing a supernova within that galaxy, in order to estimate the age of the Universe. Explain how the speed of recession and the distance to a galaxy can together be used, via the Hubble constant, to estimate the age of the Universe.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A national science centre is creating a permanent exhibit explaining the vast scale of the Universe, the discovery of cosmic microwave background radiation, and the evidence supporting the Big Bang Theory.

   (a)

   Describe the scale of the Universe in terms of galaxies, stars and light-years, and explain, in detail, how the observation of redshift in the light from distant galaxies provides evidence that the Universe is expanding and supports the Big Bang Theory.

   [6 marks]

   (b)

   The exhibit also needs to explain how the discovery of cosmic microwave background radiation (CMBR), together with the use of the Hubble constant, has strengthened scientific confidence in the Big Bang Theory and allowed scientists to estimate the age of the Universe. Explain what CMBR is, why it is considered strong evidence for the Big Bang Theory, and describe how the Hubble constant is used, together with measurements of recession speed and distance for many galaxies, to estimate the age of the Universe.

   [6 marks]

   Total for question 4: 12 marks

End of questions