IGCSEPhysicsCambridge (CIE)Revision Notes6. Space PhysicsStars & The UniverseThe Sun as a Star

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

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Leander Oates

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:

straight H presubscript 1 presuperscript 2 space plus space straight H presubscript 1 presuperscript 3 space rightwards arrow space He presubscript 2 presuperscript 4 space plus space straight n presubscript 0 presuperscript 1

  • Where H presubscript 1 presuperscript 2 (deuterium) and straight H presubscript 1 presuperscript 3 (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.

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    Leander Oates

    Author: Leander Oates

    Expertise: Physics

    Leander graduated with First-class honours in Science and Education from Sheffield Hallam University. She won the prestigious Lord Robert Winston Solomon Lipson Prize in recognition of her dedication to science and teaching excellence. After teaching and tutoring both science and maths students, Leander now brings this passion for helping young people reach their potential to her work at SME.

    Caroline Carroll

    Author: Caroline Carroll

    Expertise: Physics Subject Lead

    Caroline graduated from the University of Nottingham with a degree in Chemistry and Molecular Physics. She spent several years working as an Industrial Chemist in the automotive industry before retraining to teach. Caroline has over 12 years of experience teaching GCSE and A-level chemistry and physics. She is passionate about creating high-quality resources to help students achieve their full potential.