A main sequence star much more massive than the Sun eventually runs out of hydrogen fuel. Describe the sequence of stages the star passes through from the point at which it leaves the main sequence until a neutron star is formed.

Pearson Edexcel International GCSE Physics (4PH1) — 8.2 Stellar evolution · Describe · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

1. The star expands massively to become a red supergiant.
2. The red supergiant explodes as a supernova.
3. The core collapses under gravity because nuclear fusion can no longer support it.
4. The collapsed core contracts to form a neutron star.

Examiner tips

  • Use the exact sequence: expansion → supernova → collapse → neutron star.
  • Show the cause of collapse (fusion stops) and the result (neutron star).
  • Keep each point brief but complete.
  • Use UK spelling (e.g., ‘neutron star’).

Common mistakes

  • Confusing the supernova with the red supergiant stage.
  • Omitting the reason for collapse (fusion stops).
  • Using the wrong final remnant (white dwarf or black hole).

Mark scheme (4 marks)

  1. The star expands (massively) to become a red supergiant
  2. The red supergiant explodes in a supernova
  3. The hydrogen fuel (or nuclear fusion) is no longer sufficient to maintain outward pressure, so the star collapses under gravity / gravitational attraction
  4. What remains after the supernova contracts / collapses to form a neutron star

Key terms in this question

main sequence star · neutron star

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