Describe the main stages in the life cycle of a star similar in mass to our Sun, starting from a nebula and ending at its final stage. Include the names of each stage in your answer.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (5 marks)
A nebula is a cloud of gas and dust that is pulled together by gravity, causing the nebula to collapse.
A protostar forms as the collapsing material heats up; the temperature rises as matter compresses.
The star becomes a main‑sequence star where hydrogen nuclei fuse to form helium (nuclear fusion).
When the core hydrogen is exhausted the star expands to become a red giant.
The red giant eventually sheds its outer layers, leaving behind a white dwarf as the final stage.
A protostar forms as the collapsing material heats up; the temperature rises as matter compresses.
The star becomes a main‑sequence star where hydrogen nuclei fuse to form helium (nuclear fusion).
When the core hydrogen is exhausted the star expands to become a red giant.
The red giant eventually sheds its outer layers, leaving behind a white dwarf as the final stage.
Examiner tips
- Use the exact stage names (nebula, protostar, main‑sequence star, red giant, white dwarf).
- Show the cause–effect sequence (gravity → collapse → heating → fusion → expansion → shedding).
- Mention hydrogen fusion in the main‑sequence stage.
Common mistakes
- Confusing a nebula with a star; not stating that the nebula collapses. Forgetting to mention the red giant stage or the shedding of outer layers. Using vague terms like “big star” instead of “red giant” or “white dwarf”.
Mark scheme (5 marks)
- A nebula is a cloud of gas and dust that is pulled together by gravity / gravitational attraction causes the nebula to collapse
- A protostar forms as the collapsing material heats up / temperature rises as matter compresses
- The star becomes a main sequence star where hydrogen nuclei fuse to form helium (nuclear fusion)
- When hydrogen runs out the star expands to become a red giant
- The red giant eventually sheds its outer layers leaving behind a white dwarf as the final stage
Key terms in this question
Related
- All Eduqas A-Level Physics revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →
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