Miss Wise's Physics Site
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Life Cycle of a Star

How a star changes over its lifetime depends on two forces: the gravitational  force pulling the star inwards and the force from the fusion pushing it outwards.

Stars begin as nebulae, clouds of dust and gas that are pulled together by gravity.

Fusion reactions begin and the become a main sequence star, like our own sun. At this point the star is fusing hydrogen to form helium.

As the fuel for fusion runs out, the star has to start fusing helium. This produces a lot more pressure and the star expands and cools, turning into a red giant. How large a giant it becomes depends on its size: if it is small, like the sun, it becomes a red giant. If it's large, it becomes a supergiant.

Picture
Large Stars

When a red supergiant runs out of fuel the force of gravity becomes much stronger than the fusion forces and so the star collapses in on itself. This sudden collapse makes it explode in a supernova. This supernova sends particles into space with immense energy. This is the only way that heavier elements such as iron and uranium can be formed. Because we have heavy elements in our solar system we know that it must have formed after a supernova: the outer layers are blasted away and can form a nebula and a new star.  The inner layers shrink down and become a very dense core.  The largest will collapse completely into a black hole and the smaller will become a neutron star.


Small Stars

When a red giant runs out of fuel for fusion, it collapses, increasing the pressure which allows it to burn brighter as a smaller white dwarf.  As this runs out of fuel, the white dwarf cools and glows red until it finally is left as a cold, black dward, a dead husk of a star. 

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  • Home
  • GCSE
    • Combined Science >
      • The History of the Universe
      • Telescopes
      • Infrasound
      • The Structure of the Earth and Seismic Waves
      • Life Cycle of a Star
      • The Big Bang Theory and The Doppler Effect
    • Radioactivity >
      • The Structure of an Atom
      • Types of Radiation
      • Uses of Radiation
      • Nuclear Fission
      • Half Life
    • Electricity >
      • Static Electricity
      • Current, Voltage, Energy
      • Circuit Symbols
      • Series and Parallel Circuits
      • Ohm's Law and Resistance
      • Alternating Current
      • Electrical Safety
      • Energy and Pricing
      • The National Grid
    • Electromagnetism >
      • Magnets and Electromagnets
      • Electromagnetic Induction
      • Motors and Generators
      • Transformers
    • Waves >
      • Sound and Ultrasound
      • Wave Properties >
        • Reflection and Refraction
        • Diffraction
        • Images in a Mirror
        • Interference
      • EM Spectrum and it's uses >
        • Radiowaves
        • Microwaves
        • Infra Red
        • Visible Light
        • UV
        • X- Rays
        • Gamma Rays
    • Forces and Motion >
      • Speed and Velocity
      • Graphs of Motion
      • Newton's Laws
      • Common Forces
      • Terminal Velocity
      • Elasticity
      • Moments
      • Circular Motion
      • Momentum
      • Car Safety
    • Particles >
      • States of Matter
      • Density
      • Pressure
      • Ideal Gases
      • Changing State and Temperature >
        • Specific Heat Capacity
        • Specific Latent Heat
      • Heat Transfer >
        • Conduction
        • Convection
        • Cooling
        • Radiation
    • Energy Resources and Energy Transfer >
      • Energy and Efficiency
      • Heat Loss In the Home
      • Gravitational Potential Energy
      • Kinetic Energy
      • Work
      • Power Stations
  • Physics Skills
    • How to Write up an Experiment >
      • Hypothesis
      • Methods
      • How to Draw a Graph
      • Results Tables
      • Conclusions
      • Evaluations
    • Mathematics >
      • Rearranging Equations
      • Substituting into Equations
      • Trigonometry
      • Errors
  • Lesson Blog
  • Apps
  • Teachers Area