GCSE level questions on the Earth in Space
Q7.
Stars go through a life cycle. Some stars will finish their life cycle as a black dwarf and other stars as a black hole.
(a) The table gives the mass, relative to the Sun, of three stars, J, K and L.
Star |
Mass of the star relative to the Sun |
J |
0.5 |
K |
14.5 |
L |
20.0 |
Which one of the stars, J, K or L, will become a black dwarf? Give a reason for your answer.
Star J 
will become a black dwarf. Our star - the Sun - and others of its size or smaller will follow the same route. K and L are much larger than our Sun, they will follow a different route.
[2 marks]
(b) Scientists can take the measurements needed to calculate the mass of many stars. Scientists cannot calculate the mass of the star Betelgeuse. They estimate that the star has a mass between 8 and 20 times the mass of the Sun.
(i) Betelgeuse is in the red super giant stage of its life cycle. What will happen to Betelgeuse at the end of the red super giant stage?
It will explode in a supernova.
[1 mark]
(ii) Suggest one reason why scientists can only estimate and not calculate the mass of Betelgeuse.
They do not have a method to measure mass of stars. They use information from the stars to make an educated guess.
[1 mark]
(iii) In the future, it may become possible for scientists to calculate the mass of Betelgeuse. Suggest one reason why.
In the future we may have developed technology and theories that will allow us to calculate the mass.
[1 mark]
(c) Describe what happens to a star, after the main sequence period, for the star to eventually become a black dwarf.
The star begins to run out of hydrogen - its fuel for the fusion process - and swells to become a red giant.When the fuel runs out completely the crushing force of gravity makes the star collapse under the force of its own weight. Such a collapsed star, at its life's end, is called a white dwarf. It will continue to shine until the kinetic energy of the atoms diminishes enough to stop radiation emission - it will then be a black dwarf - a cold mass moving through space. (5 max)
[5 marks]
(Total 10 marks)
About this site
After the stable main sequence period the star is effectively dying. How it dies depends on its size. Only small and medium stars end up being a black dwarf - very large stars undergo a supernova explosion. - see 
