Explain why a massive star, after leaving the main sequence, ends its life differently from a star of similar mass to the Sun.

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

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

Stars spend most of their lives as main sequence stars, but their ultimate fate depends on their mass.

Model answer (4 marks)

When the core H is exhausted, both stars collapse under gravity and then expand.
1. A massive star expands to a red supergiant, whereas a Sun‑like star becomes a red giant.
2. The massive star then undergoes core collapse and explodes as a supernova, dispersing heavy elements.
3. The remnant is a neutron star or black hole; a Sun‑like star ends as a white dwarf.

Examiner tips

  • Use the sequence: collapse → expansion → supernova → remnant. Mention the different remnant types. Keep the answer concise and use the exact terms from the mark scheme.

Common mistakes

  • Confusing the order of collapse and expansion. Using ‘white dwarf’ for the massive star. Omitting the supernova step.

Mark scheme (4 marks)

  1. When hydrogen is used up, both types of star initially expand / both stars collapse under gravity then expand
  2. A massive star expands to become a red supergiant (whereas a Sun-like star becomes a red giant)
  3. A massive star then explodes as a supernova, distributing elements throughout the universe
  4. After the supernova, what remains is a neutron star or black hole (whereas a Sun-like star ends as a white dwarf)

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