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Astronomy

The life cycle of a star like the Sun

  • 3 things to know
  • Paper 1

Overview

The stages from nebula and protostar to main sequence star, red giant and white dwarf, hydrogen fusing to helium, why a red giant looks red, and how gravity and thermal expansion balance in a main sequence star until its hydrogen runs out.

What you need to know

Answer each one before you reveal it.

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Key term

Describe how a star begins to form from a nebula.

Process

What must happen inside a protostar before it becomes a main sequence star?

Process

Which nuclei fuse in the core of a main sequence star, and what do they produce?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    Name the cloud of dust and gas in which stars begin to form.

    Model answer

    A nebula.

  2. 2

    Describe how a star begins to form from a nebula.

    Model answer

    Gravity pulls the dust and gas together, and the material heats up as it is squeezed into a protostar.

  3. 3

    What must happen inside a protostar before it becomes a main sequence star?

    Model answer

    The temperature and pressure must rise high enough for hydrogen nuclei to begin fusing together.

  4. 4

    Which nuclei fuse in the core of a main sequence star, and what do they produce?

    Model answer

    Hydrogen nuclei fuse together to produce helium.

  5. 5

    State, in order, the stages in the life of a star with a mass similar to that of the Sun.

    Model answer

    Nebula, protostar, main sequence star, red giant and finally white dwarf.

  6. 6

    Describe what happens to a star of similar mass to the Sun when the hydrogen in its core runs out.

    Model answer

    Its core contracts while its outer layers swell and cool, so the star becomes a red giant.

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