Trace the planetary nebula and white dwarf branch
Follow a less-massive red giant into expelled material surrounding a white dwarf remnant.
Section P6.2.2 · Stars
Exam scope and assessment notes
Mapped to the named 0973 section using teaching from the corresponding single-science course. A 0973-specific review of every Core and Supplement objective is still in progress. Written practice is self-checked; it does not demonstrate supervised laboratory competence or award an official Cambridge grade. This qualification reports two grades on the 9–1 scale; confirm the entry route for your zone and exam series.
Before you begin
- Recall the mass-dependent giant branches.
- Distinguish a gas cloud from a compact object.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which branch follows a less-massive red giant?
What you will learn
- Follow a less-massive red giant into expelled material surrounding a white dwarf remnant.
- Distinguish the planetary nebula cloud from the central remnant and from planets.
Follow the less-massive route
In the syllabus’s less-massive route, a red giant sheds outer material that forms a planetary nebula. A white dwarf remains at its centre. The cloud and remnant are different outcomes from different parts of the evolved star; the white dwarf is not the whole extended nebula.
Despite its name, a planetary nebula is not a newly created planet or the collection of ordinary planets in a Solar System. The historical name describes an observed appearance, not a planetary classification.
Keep the endpoint distinct
A white dwarf is a compact stellar remnant that can radiate stored thermal energy as it cools. Its appearance does not imply continuing central hydrogen fusion like the earlier stable stage. Nor is a Sun-like star expected to follow the massive-star supernova branch in this syllabus model.
A schematic arrow gives evolutionary ordering, not an instantaneous event or a diagram whose equal boxes measure equal durations, radii or masses. Use the initial-mass condition when selecting this route.
Sources for this lesson
Pause and explain
Is a planetary nebula a planet?
Worked example
Label the extended cloud and compact centre after a less-massive red giant sheds its outer layers.
Show the worked solution
- Identify expelled outer material.
- Name the surrounding planetary nebula.
- Name the central white dwarf remnant.
Answer Cloud: planetary nebula; centre: white dwarf.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Complete stable less-massive star → red giant → __ with __ at its centre.
Give me a hint
Identify the expelled cloud separately from the compact remnant.
Compare my reasoning
- Follow the less-massive condition.
- Name a planetary nebula as the cloud.
- Name a white dwarf at the centre.
Planetary nebula with a white dwarf at its centre.
Look for these in your work
- Name both outcomes.
- Keep cloud and centre separate.
Explain why the phrase planetary nebula does not prove a new planet has formed.
Give me a hint
Use the physical origin, not the sound of its historical name.
Compare my reasoning
- Material is shed from an evolved star.
- It forms an extended gas cloud.
- The centre is a stellar remnant, not evidence of a new planet.
It describes expelled stellar gas; the name does not establish planet formation.
Look for these in your work
- State the cloud origin.
- Avoid name-based classification.
A Sun-like star is placed on a poster ending in a supernova and black hole. Repair the route.
Give me a hint
Select the less-massive branch before choosing its endpoint.
Compare my reasoning
- Use a red-giant stage.
- Then identify a planetary nebula.
- Place a white dwarf at the centre.
Sun-like stable star → red giant → planetary nebula and central white dwarf.
Look for these in your work
- Use the correct branch.
- Include both cloud and remnant.
Common mistakes
- Planetary nebula does not mean planet.
- White dwarf and nebula are distinct.
- The Sun-like branch does not end in a massive-star supernova.
What can you explain now?
Is a planetary nebula a planet?
Compare with the explanation
No; it is expelled gas surrounding a remnant
The name does not classify the cloud as an orbiting rocky or giant planet.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Distinguish the planetary nebula cloud from the central remnant and from planets.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.