Galaxies and the UniverseIB MYP Physics: Subtopic test

1. 1
   A newspaper article reports that the Andromeda Galaxy is about 2.5 million light-years from Earth, and that our own galaxy, the Milky Way, contains over 100 billion stars.

   (a)

   What is a light-year?

   [1 mark]

   • AThe time taken for the Earth to orbit the Sun
   • BThe distance that light travels in one year
   • CThe distance from the Earth to the Sun
   • DThe brightness of a star over one year

   (b)

   What is a galaxy?

   [1 mark]

   • AA very large group of stars, gas and dust held together by gravity
   • BA group of planets that orbit one star
   • CA cloud of gas and dust in which a single star forms
   • DA star that has exploded at the end of its life

   (c)

   Explain what is meant by saying that the Andromeda Galaxy is 2.5 million light-years away, and what this means for the light we see from it.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Astronomers measure the light from several distant galaxies. In each case, the pattern of dark lines in the spectrum is found at longer wavelengths than the same pattern from a laboratory source. The more distant the galaxy, the greater the shift in wavelength.

   (a)

   What name is given to this increase in the wavelength of light from distant galaxies?

   [1 mark]

   • ABlue shift
   • BRefraction
   • CReflection
   • DRed shift

   (b)

   What does the red shift tell astronomers about most distant galaxies?

   [1 mark]

   • AThey are moving towards us
   • BThey are not moving
   • CThey are moving away from us
   • DThey are shrinking in size

   (c)

   Explain how the fact that the shift is greater for more distant galaxies supports the idea that the Universe is expanding.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   In 1965 two radio engineers in the USA detected a faint microwave signal arriving equally from every direction in the sky. It was later identified as radiation left over from the early Universe.

   (a)

   Describe the Big Bang theory.

   [3 marks]

   (b)

   Explain how red shift and the microwave signal give evidence for the Big Bang theory.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Astronomers measure how fast stars orbit the centre of a spiral galaxy. Calculations using the visible stars and gas predict that stars near the edge should move much more slowly than stars near the centre. Measurements show that stars near the edge move at almost the same speed as stars near the centre. Astronomers suggest that dark matter, which gives out no light, provides extra gravity. Separately, a group of countries has proposed building a very large array of radio telescopes in a remote desert. The site would need a large radio-quiet zone in which mobile phone and Wi-Fi transmitters are banned.

   (a)

   Describe the evidence that led astronomers to suggest dark matter, explain how dark matter would account for it, and evaluate whether the evidence proves that dark matter exists.

   [6 marks]

   (b)

   Discuss and evaluate whether the countries should build the radio telescope array.

   [6 marks]

   Total for question 4: 12 marks

End of questions