The Sun as a Star (Cambridge (CIE) IGCSE Physics)

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Written by: Leander Oates

Reviewed by: Caroline Carroll

The Sun as a star

The Sun is a medium-sized star which lies at the centre of the Solar System
It consists mostly of the two elements hydrogen and helium
It radiates most of its energy in the infrared, visible and ultraviolet regions of the electromagnetic spectrum

Our Sun

The Sun, downloadable IGCSE & GCSE Physics revision notes

The Sun is a medium-sized star consisting of mostly hydrogen and helium

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Nuclear fusion in stars

Extended tier only

Stars are huge balls of (mostly) hydrogen gas
In the centre of a star, hydrogen nuclei undergo nuclear fusion to form helium nuclei
An equation for a possible fusion reaction is:

${}_{1}^{2}H + {}_{1}^{3}H \to {}_{2}^{4}{He} + {}_{0}^{1}n$

Where ${}_{1}^{2}H$ (deuterium) and ${}_{1}^{3}H$ (tritium) are both isotopes of hydrogen
- These are formed through other fusion reactions in the star

A huge amount of energy is released in the reaction
All stable stars are powered by nuclear fusion reactions

Examiner Tips and Tricks

It is useful to remember that hydrogen is the fuel within stars, but the details of the reaction between deuterium and tritium is not required at this level.

Last updated: 1 October 2024

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