Main Sequence Stars and the Sun

This lesson covers the properties of main sequence stars and the Sun in detail — as required by the Edexcel GCSE Physics specification (1PH0), Topic 7: Astronomy. This is a Paper 2 topic. You need to understand how the Sun produces energy, the relationship between a star's mass, temperature, luminosity and lifetime, and have awareness of the Hertzsprung-Russell diagram.

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The Sun — A Typical Main Sequence Star

The Sun is classified as a main sequence star. It is a medium-sized star roughly halfway through its expected lifetime.

Property	Value
Age	Approximately 4.6 billion years old
Expected total lifetime	Approximately 10 billion years
Time remaining	Approximately 5 billion years
Core temperature	Approximately 15 million °C
Surface temperature	Approximately 5,500 °C
Composition	Mainly hydrogen (~73%) and helium (~25%)
Diameter	Approximately 1.4 million km (109 × Earth's diameter)
Mass	Approximately 2 × 10³⁰ kg (330,000 × Earth's mass)