Stars and their life cycleIB MYP Physics: Subtopic test

1. 1
   A planetarium presenter in Dubai explains that every star begins life inside a vast cloud of gas and dust called a nebula, and that the Sun is now about halfway through a long, stable period of its life.

   (a)

   Which force pulls the gas and dust in a nebula together to form a protostar?

   [1 mark]

   • AGravity
   • BMagnetic force
   • CFriction
   • DElectrostatic repulsion between particles

   (b)

   Which process releases energy in the core of the Sun?

   [1 mark]

   • ANuclear fission of uranium nuclei
   • BBurning of hydrogen in oxygen
   • CNuclear fusion of hydrogen nuclei to form helium
   • DRadioactive decay of heavy elements

   (c)

   Explain why the Sun stays the same size for billions of years.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Astronomers compare the future of the Sun with that of Betelgeuse, a red supergiant star that is about 15 times more massive than the Sun. They predict very different endings for the two stars.

   (a)

   What will the Sun become after it has been a red giant?

   [1 mark]

   • AA neutron star
   • BA white dwarf
   • CA black hole
   • DA supernova

   (b)

   What is the most likely end of Betelgeuse as a normal star?

   [1 mark]

   • AIt will fade slowly into a white dwarf
   • BIt will shrink back into a protostar
   • CIt will turn into a planet
   • DIt will explode as a supernova

   (c)

   Compare the end of the Sun's life with the end of Betelgeuse's life.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Chemists have found that the iron in blood, the calcium in bones and the oxygen we breathe were not present in the early Universe, which contained almost only hydrogen and helium. Astronomers say that we are made of the material of old stars.

   (a)

   Describe how elements heavier than hydrogen and helium are made.

   [3 marks]

   (b)

   Explain how elements made in a star came to be part of the Earth and living things.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A research team collects approximate data on how long stars stay on the main sequence. A star with half the mass of the Sun lasts about 60 billion years, a star with the same mass as the Sun lasts about 10 billion years, and a star with 10 times the mass of the Sun lasts about 30 million years. A coastal town in Spain is also asked to join a dark-sky scheme. Street and sign lighting would be switched off or dimmed after 11 pm so that the stars can be seen clearly.

   (a)

   Describe the pattern in the data. Calculate how many times shorter the main sequence of the 10-solar-mass star is than that of the Sun, explain the pattern, predict whether a star with twice the Sun's mass would last longer or shorter than 10 billion years, and suggest one limitation of the data.

   [6 marks]

   (b)

   Discuss and evaluate whether the town should join the dark-sky scheme.

   [6 marks]

   Total for question 4: 12 marks

End of questions