Revise GCSE Physics


Question:Describe the life cycle of a small star, such as the Sun.

The Sun is a small star.

Stars up to three times as massive as the Sun are classed as 'small' stars.

We expect the second part of the lifecycle of a small start to proceed as follows:

At the end of the Main Sequence stage the star runs out of Hydrogen for Nuclear Fusion.

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The Star grows bigger and becomes a Red Giant star.

The star continues to produce energy by Nuclear fusion but now it is helium and then even heavier elements that are being fused together.

Eventually, elements as heavy as Iron are produced inside stars by Nuclear Fusion.

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Once fusion of heavier elements becomes impossible, smaller stars explode into Planetary Nebula, which often have a White Dwarf star at the centre.

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These images show Planetary Nebula with a White Dwarf star near the centre.

NB. A Planetary Nebula has nothing to do with Planets!!

The White Dwarf star cannot generate further energy by nuclear fusion, and so it cools and fades to become a Black dwarf and ends its lifecycle as a lump of cooling steller matter.