IGCSEPhysics: Co-ordinated Sciences (Double Award)CIERevision Notes6. Space PhysicsStars & the UniverseThe Sun as a Star

The Sun as a Star (CIE IGCSE Physics: Co-ordinated Sciences (Double Award))

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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 Tip

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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    Katie M

    Author: Katie M

    Expertise: Physics

    Katie has always been passionate about the sciences, and completed a degree in Astrophysics at Sheffield University. She decided that she wanted to inspire other young people, so moved to Bristol to complete a PGCE in Secondary Science. She particularly loves creating fun and absorbing materials to help students achieve their exam potential.